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How to Cite Sources

Here is a complete list for how to cite sources. Most of these guides present citation guidance and examples in MLA, APA, and Chicago.

If you’re looking for general information on MLA or APA citations , the EasyBib Writing Center was designed for you! It has articles on what’s needed in an MLA in-text citation , how to format an APA paper, what an MLA annotated bibliography is, making an MLA works cited page, and much more!

MLA Format Citation Examples

The Modern Language Association created the MLA Style, currently in its 9th edition, to provide researchers with guidelines for writing and documenting scholarly borrowings.  Most often used in the humanities, MLA style (or MLA format ) has been adopted and used by numerous other disciplines, in multiple parts of the world.

MLA provides standard rules to follow so that most research papers are formatted in a similar manner. This makes it easier for readers to comprehend the information. The MLA in-text citation guidelines, MLA works cited standards, and MLA annotated bibliography instructions provide scholars with the information they need to properly cite sources in their research papers, articles, and assignments.

  • Book Chapter
  • Conference Paper
  • Documentary
  • Encyclopedia
  • Google Images
  • Kindle Book
  • Memorial Inscription
  • Museum Exhibit
  • Painting or Artwork
  • PowerPoint Presentation
  • Sheet Music
  • Thesis or Dissertation
  • YouTube Video

APA Format Citation Examples

The American Psychological Association created the APA citation style in 1929 as a way to help psychologists, anthropologists, and even business managers establish one common way to cite sources and present content.

APA is used when citing sources for academic articles such as journals, and is intended to help readers better comprehend content, and to avoid language bias wherever possible. The APA style (or APA format ) is now in its 7th edition, and provides citation style guides for virtually any type of resource.

Chicago Style Citation Examples

The Chicago/Turabian style of citing sources is generally used when citing sources for humanities papers, and is best known for its requirement that writers place bibliographic citations at the bottom of a page (in Chicago-format footnotes ) or at the end of a paper (endnotes).

The Turabian and Chicago citation styles are almost identical, but the Turabian style is geared towards student published papers such as theses and dissertations, while the Chicago style provides guidelines for all types of publications. This is why you’ll commonly see Chicago style and Turabian style presented together. The Chicago Manual of Style is currently in its 17th edition, and Turabian’s A Manual for Writers of Research Papers, Theses, and Dissertations is in its 8th edition.

Citing Specific Sources or Events

  • Declaration of Independence
  • Gettysburg Address
  • Martin Luther King Jr. Speech
  • President Obama’s Farewell Address
  • President Trump’s Inauguration Speech
  • White House Press Briefing

Additional FAQs

  • Citing Archived Contributors
  • Citing a Blog
  • Citing a Book Chapter
  • Citing a Source in a Foreign Language
  • Citing an Image
  • Citing a Song
  • Citing Special Contributors
  • Citing a Translated Article
  • Citing a Tweet

6 Interesting Citation Facts

The world of citations may seem cut and dry, but there’s more to them than just specific capitalization rules, MLA in-text citations , and other formatting specifications. Citations have been helping researches document their sources for hundreds of years, and are a great way to learn more about a particular subject area.

Ever wonder what sets all the different styles apart, or how they came to be in the first place? Read on for some interesting facts about citations!

1. There are Over 7,000 Different Citation Styles

You may be familiar with MLA and APA citation styles, but there are actually thousands of citation styles used for all different academic disciplines all across the world. Deciding which one to use can be difficult, so be sure to ask you instructor which one you should be using for your next paper.

2. Some Citation Styles are Named After People

While a majority of citation styles are named for the specific organizations that publish them (i.e. APA is published by the American Psychological Association, and MLA format is named for the Modern Language Association), some are actually named after individuals. The most well-known example of this is perhaps Turabian style, named for Kate L. Turabian, an American educator and writer. She developed this style as a condensed version of the Chicago Manual of Style in order to present a more concise set of rules to students.

3. There are Some Really Specific and Uniquely Named Citation Styles

How specific can citation styles get? The answer is very. For example, the “Flavour and Fragrance Journal” style is based on a bimonthly, peer-reviewed scientific journal published since 1985 by John Wiley & Sons. It publishes original research articles, reviews and special reports on all aspects of flavor and fragrance. Another example is “Nordic Pulp and Paper Research,” a style used by an international scientific magazine covering science and technology for the areas of wood or bio-mass constituents.

4. More citations were created on  EasyBib.com  in the first quarter of 2018 than there are people in California.

The US Census Bureau estimates that approximately 39.5 million people live in the state of California. Meanwhile, about 43 million citations were made on EasyBib from January to March of 2018. That’s a lot of citations.

5. “Citations” is a Word With a Long History

The word “citations” can be traced back literally thousands of years to the Latin word “citare” meaning “to summon, urge, call; put in sudden motion, call forward; rouse, excite.” The word then took on its more modern meaning and relevance to writing papers in the 1600s, where it became known as the “act of citing or quoting a passage from a book, etc.”

6. Citation Styles are Always Changing

The concept of citations always stays the same. It is a means of preventing plagiarism and demonstrating where you relied on outside sources. The specific style rules, however, can and do change regularly. For example, in 2018 alone, 46 new citation styles were introduced , and 106 updates were made to exiting styles. At EasyBib, we are always on the lookout for ways to improve our styles and opportunities to add new ones to our list.

Why Citations Matter

Here are the ways accurate citations can help your students achieve academic success, and how you can answer the dreaded question, “why should I cite my sources?”

They Give Credit to the Right People

Citing their sources makes sure that the reader can differentiate the student’s original thoughts from those of other researchers. Not only does this make sure that the sources they use receive proper credit for their work, it ensures that the student receives deserved recognition for their unique contributions to the topic. Whether the student is citing in MLA format , APA format , or any other style, citations serve as a natural way to place a student’s work in the broader context of the subject area, and serve as an easy way to gauge their commitment to the project.

They Provide Hard Evidence of Ideas

Having many citations from a wide variety of sources related to their idea means that the student is working on a well-researched and respected subject. Citing sources that back up their claim creates room for fact-checking and further research . And, if they can cite a few sources that have the converse opinion or idea, and then demonstrate to the reader why they believe that that viewpoint is wrong by again citing credible sources, the student is well on their way to winning over the reader and cementing their point of view.

They Promote Originality and Prevent Plagiarism

The point of research projects is not to regurgitate information that can already be found elsewhere. We have Google for that! What the student’s project should aim to do is promote an original idea or a spin on an existing idea, and use reliable sources to promote that idea. Copying or directly referencing a source without proper citation can lead to not only a poor grade, but accusations of academic dishonesty. By citing their sources regularly and accurately, students can easily avoid the trap of plagiarism , and promote further research on their topic.

They Create Better Researchers

By researching sources to back up and promote their ideas, students are becoming better researchers without even knowing it! Each time a new source is read or researched, the student is becoming more engaged with the project and is developing a deeper understanding of the subject area. Proper citations demonstrate a breadth of the student’s reading and dedication to the project itself. By creating citations, students are compelled to make connections between their sources and discern research patterns. Each time they complete this process, they are helping themselves become better researchers and writers overall.

When is the Right Time to Start Making Citations?

Make in-text/parenthetical citations as you need them.

As you are writing your paper, be sure to include references within the text that correspond with references in a works cited or bibliography. These are usually called in-text citations or parenthetical citations in MLA and APA formats. The most effective time to complete these is directly after you have made your reference to another source. For instance, after writing the line from Charles Dickens’ A Tale of Two Cities : “It was the best of times, it was the worst of times…,” you would include a citation like this (depending on your chosen citation style):

(Dickens 11).

This signals to the reader that you have referenced an outside source. What’s great about this system is that the in-text citations serve as a natural list for all of the citations you have made in your paper, which will make completing the works cited page a whole lot easier. After you are done writing, all that will be left for you to do is scan your paper for these references, and then build a works cited page that includes a citation for each one.

Need help creating an MLA works cited page ? Try the MLA format generator on EasyBib.com! We also have a guide on how to format an APA reference page .

2. Understand the General Formatting Rules of Your Citation Style Before You Start Writing

While reading up on paper formatting may not sound exciting, being aware of how your paper should look early on in the paper writing process is super important. Citation styles can dictate more than just the appearance of the citations themselves, but rather can impact the layout of your paper as a whole, with specific guidelines concerning margin width, title treatment, and even font size and spacing. Knowing how to organize your paper before you start writing will ensure that you do not receive a low grade for something as trivial as forgetting a hanging indent.

Don’t know where to start? Here’s a formatting guide on APA format .

3. Double-check All of Your Outside Sources for Relevance and Trustworthiness First

Collecting outside sources that support your research and specific topic is a critical step in writing an effective paper. But before you run to the library and grab the first 20 books you can lay your hands on, keep in mind that selecting a source to include in your paper should not be taken lightly. Before you proceed with using it to backup your ideas, run a quick Internet search for it and see if other scholars in your field have written about it as well. Check to see if there are book reviews about it or peer accolades. If you spot something that seems off to you, you may want to consider leaving it out of your work. Doing this before your start making citations can save you a ton of time in the long run.

Finished with your paper? It may be time to run it through a grammar and plagiarism checker , like the one offered by EasyBib Plus. If you’re just looking to brush up on the basics, our grammar guides  are ready anytime you are.

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Citation Basics

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  • Find Sources through the Library
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  • Evaluate, Write & Cite

Cite your sources

  • is the right thing to do  to give credit to those who had the idea
  • shows that you have read and understand  what experts have had to say about your topic
  • helps people find the sources  that you used in case they want to read more about the topic
  • provides   evidence  for your arguments
  • is professional and  standard practice   for students and scholars

What is a Citation?

A citation identifies for the reader the original source for an idea, information, or image that is referred to in a work.

  • In the body of a paper, the  in-text citation  acknowledges the source of information used.
  • At the end of a paper, the citations are compiled on a  References  or  Works Cited  list. A basic citation includes the author, title, and publication information of the source. 

Citation basics

From:  Lemieux  Library,  University  of Seattle 

Why Should You Cite?

Quoting Are you quoting two or more consecutive words from a source? Then the original source should be cited and the words or phrase placed in quotes. 

Paraphrasing If an idea or information comes from another source,  even if you put it in your own words , you still need to credit the source.  General vs. Unfamiliar Knowledge You do not need to cite material which is accepted common knowledge. If in doubt whether your information is common knowledge or not, cite it. Formats We usually think of books and articles. However, if you use material from web sites, films, music, graphs, tables, etc. you'll also need to cite these as well.

Plagiarism is presenting the words or ideas of someone else as your own without proper acknowledgment of the source. When you work on a research paper and use supporting material from works by others, it's okay to quote people and use their ideas, but you do need to correctly credit them. Even when you summarize or paraphrase information found in books, articles, or Web pages, you must acknowledge the original author.

Citation Style Help

Helpful links:

  • MLA ,  Works Cited : A Quick Guide (a template of core elements)
  • CSE  (Council of Science Editors)

For additional writing resources specific to styles listed here visit the  Purdue OWL Writing Lab

Citation and Bibliography Resources

Writing an annotated bibliography

  • How to Write an Annotated Bibliography
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The land acknowledgement used at UC Santa Cruz was developed in partnership with the Amah Mutsun Tribal Band Chairman and the Amah Mutsun Relearning Program at the UCSC Arboretum .

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A Quick Guide to Referencing | Cite Your Sources Correctly

Referencing means acknowledging the sources you have used in your writing. Including references helps you support your claims and ensures that you avoid plagiarism .

There are many referencing styles, but they usually consist of two things:

  • A citation wherever you refer to a source in your text.
  • A reference list or bibliography at the end listing full details of all your sources.

The most common method of referencing in UK universities is Harvard style , which uses author-date citations in the text. Our free Harvard Reference Generator automatically creates accurate references in this style.

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Table of contents

Referencing styles, citing your sources with in-text citations, creating your reference list or bibliography, harvard referencing examples, frequently asked questions about referencing.

Each referencing style has different rules for presenting source information. For in-text citations, some use footnotes or endnotes , while others include the author’s surname and date of publication in brackets in the text.

The reference list or bibliography is presented differently in each style, with different rules for things like capitalisation, italics, and quotation marks in references.

Your university will usually tell you which referencing style to use; they may even have their own unique style. Always follow your university’s guidelines, and ask your tutor if you are unsure. The most common styles are summarised below.

Harvard referencing, the most commonly used style at UK universities, uses author–date in-text citations corresponding to an alphabetical bibliography or reference list at the end.

Harvard Referencing Guide

Vancouver referencing, used in biomedicine and other sciences, uses reference numbers in the text corresponding to a numbered reference list at the end.

Vancouver Referencing Guide

APA referencing, used in the social and behavioural sciences, uses author–date in-text citations corresponding to an alphabetical reference list at the end.

APA Referencing Guide APA Reference Generator

MHRA referencing, used in the humanities, uses footnotes in the text with source information, in addition to an alphabetised bibliography at the end.

MHRA Referencing Guide

OSCOLA referencing, used in law, uses footnotes in the text with source information, and an alphabetical bibliography at the end in longer texts.

OSCOLA Referencing Guide

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In-text citations should be used whenever you quote, paraphrase, or refer to information from a source (e.g. a book, article, image, website, or video).

Quoting and paraphrasing

Quoting is when you directly copy some text from a source and enclose it in quotation marks to indicate that it is not your own writing.

Paraphrasing is when you rephrase the original source into your own words. In this case, you don’t use quotation marks, but you still need to include a citation.

In most referencing styles, page numbers are included when you’re quoting or paraphrasing a particular passage. If you are referring to the text as a whole, no page number is needed.

In-text citations

In-text citations are quick references to your sources. In Harvard referencing, you use the author’s surname and the date of publication in brackets.

Up to three authors are included in a Harvard in-text citation. If the source has more than three authors, include the first author followed by ‘ et al. ‘

The point of these citations is to direct your reader to the alphabetised reference list, where you give full information about each source. For example, to find the source cited above, the reader would look under ‘J’ in your reference list to find the title and publication details of the source.

Placement of in-text citations

In-text citations should be placed directly after the quotation or information they refer to, usually before a comma or full stop. If a sentence is supported by multiple sources, you can combine them in one set of brackets, separated by a semicolon.

If you mention the author’s name in the text already, you don’t include it in the citation, and you can place the citation immediately after the name.

  • Another researcher warns that the results of this method are ‘inconsistent’ (Singh, 2018, p. 13) .
  • Previous research has frequently illustrated the pitfalls of this method (Singh, 2018; Jones, 2016) .
  • Singh (2018, p. 13) warns that the results of this method are ‘inconsistent’.

The terms ‘bibliography’ and ‘reference list’ are sometimes used interchangeably. Both refer to a list that contains full information on all the sources cited in your text. Sometimes ‘bibliography’ is used to mean a more extensive list, also containing sources that you consulted but did not cite in the text.

A reference list or bibliography is usually mandatory, since in-text citations typically don’t provide full source information. For styles that already include full source information in footnotes (e.g. OSCOLA and Chicago Style ), the bibliography is optional, although your university may still require you to include one.

Format of the reference list

Reference lists are usually alphabetised by authors’ last names. Each entry in the list appears on a new line, and a hanging indent is applied if an entry extends onto multiple lines.

Harvard reference list example

Different source information is included for different source types. Each style provides detailed guidelines for exactly what information should be included and how it should be presented.

Below are some examples of reference list entries for common source types in Harvard style.

  • Chapter of a book
  • Journal article

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Your university should tell you which referencing style to follow. If you’re unsure, check with a supervisor. Commonly used styles include:

  • Harvard referencing , the most commonly used style in UK universities.
  • MHRA , used in humanities subjects.
  • APA , used in the social sciences.
  • Vancouver , used in biomedicine.
  • OSCOLA , used in law.

Your university may have its own referencing style guide.

If you are allowed to choose which style to follow, we recommend Harvard referencing, as it is a straightforward and widely used style.

References should be included in your text whenever you use words, ideas, or information from a source. A source can be anything from a book or journal article to a website or YouTube video.

If you don’t acknowledge your sources, you can get in trouble for plagiarism .

To avoid plagiarism , always include a reference when you use words, ideas or information from a source. This shows that you are not trying to pass the work of others off as your own.

You must also properly quote or paraphrase the source. If you’re not sure whether you’ve done this correctly, you can use the Scribbr Plagiarism Checker to find and correct any mistakes.

Harvard referencing uses an author–date system. Sources are cited by the author’s last name and the publication year in brackets. Each Harvard in-text citation corresponds to an entry in the alphabetised reference list at the end of the paper.

Vancouver referencing uses a numerical system. Sources are cited by a number in parentheses or superscript. Each number corresponds to a full reference at the end of the paper.

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Citing sources: Overview

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If you have questions after consulting this guide about how to cite, please contact your advisor/professor or the writing and communication center .

Why citing is important

It's important to cite sources you used in your research for several reasons:

  • To show your reader you've done proper research by listing sources you used to get your information
  • To be a responsible scholar by giving credit to other researchers and acknowledging their ideas
  • To avoid plagiarism by quoting words and ideas used by other authors
  • To allow your reader to track down the sources you used by citing them accurately in your paper by way of footnotes, a bibliography or reference list

About citations

Citing a source means that you show, within the body of your text, that you took words, ideas, figures, images, etc. from another place.

Citations are a short way to uniquely identify a published work (e.g. book, article, chapter, web site).  They are found in bibliographies and reference lists and are also collected in article and book databases.

Citations consist of standard elements, and contain all the information necessary to identify and track down publications, including:

  • author name(s)
  • titles of books, articles, and journals
  • date of publication
  • page numbers
  • volume and issue numbers (for articles)

Citations may look different, depending on what is being cited and which style was used to create them. Choose an appropriate style guide for your needs.  Here is an example of an article citation using four different citation styles.  Notice the common elements as mentioned above:

Author - R. Langer

Article Title - New Methods of Drug Delivery

Source Title - Science

Volume and issue - Vol 249, issue 4976

Publication Date - 1990

Page numbers - 1527-1533

American Chemical Society (ACS) style:

Langer, R. New Methods of Drug Delivery. Science 1990 , 249 , 1527-1533.

IEEE Style:

R. Langer, " New Methods of Drug Delivery," Science , vol. 249 , pp. 1527-1533 , SEP 28, 1990 .

American Psychological Association   (APA) style:

Langer, R. (1990) . New methods of drug delivery. Science , 249 (4976), 1527-1533.

Modern Language Association (MLA) style:

Langer, R. " New Methods of Drug Delivery." Science 249.4976 (1990) : 1527-33.

What to cite

You must cite:

  • Facts, figures, ideas, or other information that is not common knowledge

Publications that must be cited include:  books, book chapters, articles, web pages, theses, etc.

Another person's exact words should be quoted and cited to show proper credit 

When in doubt, be safe and cite your source!

Avoiding plagiarism

Plagiarism occurs when you borrow another's words (or ideas) and do not acknowledge that you have done so. In this culture, we consider our words and ideas intellectual property; like a car or any other possession, we believe our words belong to us and cannot be used without our permission.

Plagiarism is a very serious offense. If it is found that you have plagiarized -- deliberately or inadvertently -- you may face serious consequences. In some instances, plagiarism has meant that students have had to leave the institutions where they were studying.

The best way to avoid plagiarism is to cite your sources - both within the body of your paper and in a bibliography of sources you used at the end of your paper.

Some useful links about plagiarism:

  • MIT Academic Integrity Overview on citing sources and avoiding plagiarism at MIT.
  • Avoiding Plagiarism From the MIT Writing and Communication Center.
  • Plagiarism: What It is and How to Recognize and Avoid It From Indiana University's Writing Tutorial Services.
  • Plagiarism- Overview A resource from Purdue University.
  • Next: Citation style guides >>
  • Last Updated: Jan 16, 2024 7:02 AM
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  • When neither the author nor the page number is mentioned in the body of the sentence, you should include both the author’s last name and the page number in the parenthetical citation.

Colleges and universities need to create policies that foster inclusion for low-income students (Jack 24).

  • When the author’s name is mentioned in the sentence, you should include only the page number in your parenthetical citation.

As Anthony Jack argues, colleges and universities need to create policies that foster inclusion for low-income students (24).

  • If the source you are writing about does not have page numbers, or if you consulted an e-book version of the source, you should include only the author’s name in the parenthetical citation:

Colleges and universities need to create policies that foster inclusion for low-income students (Jack).

  • If you mention the author in the body of the sentence and there is no page number in the source, you should not include a parenthetical citation.

As Anthony Jack argues, colleges and universities need to create policies that foster inclusion for low-income students.

  • If you are referring to an entire work rather than a specific page, you do not need to include a page number.

In The Privileged Poor, Anthony Jack describes many obstacles that low-income students face at selective colleges and universities.

  • If you are referring to a source that has no listed author, you should include the title (or a shortened version of the title) in your parenthetical citation.

Harvard College promises “to educate the citizens and citizen-leaders for our society” (“Mission, Vision, & History”).

  • If you are referring to a source that has two authors, you should include both authors in your parenthetical citation.

The researchers tested whether an intervention during the first year of college could improve student well-being (Walton and Cohen 1448).

  • If you refer to a source that has more than two authors, you should include the first author’s name followed by et al. ( Et al. is an abbreviation for et alia which means “and others” in Latin.) When you use et al. in a citation, you should not put it in italics.

The researchers studied more than 12,000 students who were interested in STEM fields (LaCosse et al. 8).

  • If you refer to more than one source by the same author in your paper, you should include the title (or a shortened version of the title) in your parenthetical citation so that readers will know which source to look for in your Works Cited list. If you mention the author’s name in the sentence, you only need to include the title and page number. If you mention the author and title in the sentence, you only need to include the page number.

Colleges and universities need to create policies that foster inclusion for low-income students (Jack, Privileged Poor 24).

According to Anthony Jack, colleges and universities need to create policies that foster inclusion for low-income students ( Privileged Poor 24).

As Anthony Jack writes in Privileged Poor, colleges and universities need to create policies that foster inclusion for low-income students (24).

  • If you want to credit multiple authors for making the same point, you can include them all in one parenthetical citation. 

Students who possess cultural capital, measured by proxies like involvement in literature, art, and classical music, tend to perform better in school (Bourdieu and Passeron; Dumais; Orr).

  • If you refer to a source that includes line numbers in the margins, numbered paragraphs, numbered chapters, or numbered sections rather than page numbers, you should include the number in your parenthetical citation, along with “line,” “ch./ chs.,” or “sec./secs.”   You can include stable numbering like chapters even when there are no stable page numbers (as in an e-book). You should separate “line” or other designation from the work’s title or author’s name with a comma.  If the source does not include this type of numbering, you should not include it either.

We learn that when he went to the store to buy clothes for his son, “a frantic inspection of the boys’ department revealed no suits to fit the new-born Button” (Fitzgerald, ch.2).

  • If you are citing a play, you should include the act and scene along with line numbers (for verse) or page numbers, followed by act and scene, (for prose).

Guildenstern tells Hamlet that “there has been much throwing about of brains” (Shakespeare, 2.2. 381-382).

Chris is in this mindset when he says, “a couple minutes, and your whole life changes, that’s it. It’s gone” (Nottage, 13; act 1, scene1).

  • If you are referring to a video or audio recording that contains time stamps, you should include the time in your parenthetical citation to make it easy for your readers to find the part of the recording that you are citing.

In the Stranger Things official trailer, the audience knows that something unusual is going to happen from the moment the boys get on their bicycles to ride off into the night (0:16).

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Home » How to Cite Research Paper – All Formats and Examples

How to Cite Research Paper – All Formats and Examples

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Research Paper Citation

Research Paper Citation

Research paper citation refers to the act of acknowledging and referencing a previously published work in a scholarly or academic paper . When citing sources, researchers provide information that allows readers to locate the original source, validate the claims or arguments made in the paper, and give credit to the original author(s) for their work.

The citation may include the author’s name, title of the publication, year of publication, publisher, and other relevant details that allow readers to trace the source of the information. Proper citation is a crucial component of academic writing, as it helps to ensure accuracy, credibility, and transparency in research.

How to Cite Research Paper

There are several formats that are used to cite a research paper. Follow the guide for the Citation of a Research Paper:

Last Name, First Name. Title of Book. Publisher, Year of Publication.

Example : Smith, John. The History of the World. Penguin Press, 2010.

Journal Article

Last Name, First Name. “Title of Article.” Title of Journal, vol. Volume Number, no. Issue Number, Year of Publication, pp. Page Numbers.

Example : Johnson, Emma. “The Effects of Climate Change on Agriculture.” Environmental Science Journal, vol. 10, no. 2, 2019, pp. 45-59.

Research Paper

Last Name, First Name. “Title of Paper.” Conference Name, Location, Date of Conference.

Example : Garcia, Maria. “The Importance of Early Childhood Education.” International Conference on Education, Paris, 5-7 June 2018.

Author’s Last Name, First Name. “Title of Webpage.” Website Title, Publisher, Date of Publication, URL.

Example : Smith, John. “The Benefits of Exercise.” Healthline, Healthline Media, 1 March 2022, https://www.healthline.com/health/benefits-of-exercise.

News Article

Last Name, First Name. “Title of Article.” Name of Newspaper, Date of Publication, URL.

Example : Robinson, Sarah. “Biden Announces New Climate Change Policies.” The New York Times, 22 Jan. 2021, https://www.nytimes.com/2021/01/22/climate/biden-climate-change-policies.html.

Author, A. A. (Year of publication). Title of book. Publisher.

Example: Smith, J. (2010). The History of the World. Penguin Press.

Author, A. A., Author, B. B., & Author, C. C. (Year of publication). Title of article. Title of Journal, volume number(issue number), page range.

Example: Johnson, E., Smith, K., & Lee, M. (2019). The Effects of Climate Change on Agriculture. Environmental Science Journal, 10(2), 45-59.

Author, A. A. (Year of publication). Title of paper. In Editor First Initial. Last Name (Ed.), Title of Conference Proceedings (page numbers). Publisher.

Example: Garcia, M. (2018). The Importance of Early Childhood Education. In J. Smith (Ed.), Proceedings from the International Conference on Education (pp. 60-75). Springer.

Author, A. A. (Year, Month Day of publication). Title of webpage. Website name. URL

Example: Smith, J. (2022, March 1). The Benefits of Exercise. Healthline. https://www.healthline.com/health/benefits-of-exercise

Author, A. A. (Year, Month Day of publication). Title of article. Newspaper name. URL.

Example: Robinson, S. (2021, January 22). Biden Announces New Climate Change Policies. The New York Times. https://www.nytimes.com/2021/01/22/climate/biden-climate-change-policies.html

Chicago/Turabian style

Please note that there are two main variations of the Chicago style: the author-date system and the notes and bibliography system. I will provide examples for both systems below.

Author-Date system:

  • In-text citation: (Author Last Name Year, Page Number)
  • Reference list: Author Last Name, First Name. Year. Title of Book. Place of publication: Publisher.
  • In-text citation: (Smith 2005, 28)
  • Reference list: Smith, John. 2005. The History of America. New York: Penguin Press.

Notes and Bibliography system:

  • Footnote/Endnote citation: Author First Name Last Name, Title of Book (Place of publication: Publisher, Year), Page Number.
  • Bibliography citation: Author Last Name, First Name. Title of Book. Place of publication: Publisher, Year.
  • Footnote/Endnote citation: John Smith, The History of America (New York: Penguin Press, 2005), 28.
  • Bibliography citation: Smith, John. The History of America. New York: Penguin Press, 2005.

JOURNAL ARTICLES:

  • Reference list: Author Last Name, First Name. Year. “Article Title.” Journal Title Volume Number (Issue Number): Page Range.
  • In-text citation: (Johnson 2010, 45)
  • Reference list: Johnson, Mary. 2010. “The Impact of Social Media on Society.” Journal of Communication 60(2): 39-56.
  • Footnote/Endnote citation: Author First Name Last Name, “Article Title,” Journal Title Volume Number, Issue Number (Year): Page Range.
  • Bibliography citation: Author Last Name, First Name. “Article Title.” Journal Title Volume Number, Issue Number (Year): Page Range.
  • Footnote/Endnote citation: Mary Johnson, “The Impact of Social Media on Society,” Journal of Communication 60, no. 2 (2010): 39-56.
  • Bibliography citation: Johnson, Mary. “The Impact of Social Media on Society.” Journal of Communication 60, no. 2 (2010): 39-56.

RESEARCH PAPERS:

  • Reference list: Author Last Name, First Name. Year. “Title of Paper.” Conference Proceedings Title, Location, Date. Publisher, Page Range.
  • In-text citation: (Jones 2015, 12)
  • Reference list: Jones, David. 2015. “The Effects of Climate Change on Agriculture.” Proceedings of the International Conference on Climate Change, Paris, France, June 1-3, 2015. Springer, 10-20.
  • Footnote/Endnote citation: Author First Name Last Name, “Title of Paper,” Conference Proceedings Title, Location, Date (Place of publication: Publisher, Year), Page Range.
  • Bibliography citation: Author Last Name, First Name. “Title of Paper.” Conference Proceedings Title, Location, Date. Place of publication: Publisher, Year.
  • Footnote/Endnote citation: David Jones, “The Effects of Climate Change on Agriculture,” Proceedings of the International Conference on Climate Change, Paris, France, June 1-3, 2015 (New York: Springer, 10-20).
  • Bibliography citation: Jones, David. “The Effects of Climate Change on Agriculture.” Proceedings of the International Conference on Climate Change, Paris, France, June 1-3, 2015. New York: Springer, 10-20.
  • In-text citation: (Author Last Name Year)
  • Reference list: Author Last Name, First Name. Year. “Title of Webpage.” Website Name. URL.
  • In-text citation: (Smith 2018)
  • Reference list: Smith, John. 2018. “The Importance of Recycling.” Environmental News Network. https://www.enn.com/articles/54374-the-importance-of-recycling.
  • Footnote/Endnote citation: Author First Name Last Name, “Title of Webpage,” Website Name, URL (accessed Date).
  • Bibliography citation: Author Last Name, First Name. “Title of Webpage.” Website Name. URL (accessed Date).
  • Footnote/Endnote citation: John Smith, “The Importance of Recycling,” Environmental News Network, https://www.enn.com/articles/54374-the-importance-of-recycling (accessed April 8, 2023).
  • Bibliography citation: Smith, John. “The Importance of Recycling.” Environmental News Network. https://www.enn.com/articles/54374-the-importance-of-recycling (accessed April 8, 2023).

NEWS ARTICLES:

  • Reference list: Author Last Name, First Name. Year. “Title of Article.” Name of Newspaper, Month Day.
  • In-text citation: (Johnson 2022)
  • Reference list: Johnson, Mary. 2022. “New Study Finds Link Between Coffee and Longevity.” The New York Times, January 15.
  • Footnote/Endnote citation: Author First Name Last Name, “Title of Article,” Name of Newspaper (City), Month Day, Year.
  • Bibliography citation: Author Last Name, First Name. “Title of Article.” Name of Newspaper (City), Month Day, Year.
  • Footnote/Endnote citation: Mary Johnson, “New Study Finds Link Between Coffee and Longevity,” The New York Times (New York), January 15, 2022.
  • Bibliography citation: Johnson, Mary. “New Study Finds Link Between Coffee and Longevity.” The New York Times (New York), January 15, 2022.

Harvard referencing style

Format: Author’s Last name, First initial. (Year of publication). Title of book. Publisher.

Example: Smith, J. (2008). The Art of War. Random House.

Journal article:

Format: Author’s Last name, First initial. (Year of publication). Title of article. Title of journal, volume number(issue number), page range.

Example: Brown, M. (2012). The impact of social media on business communication. Harvard Business Review, 90(12), 85-92.

Research paper:

Format: Author’s Last name, First initial. (Year of publication). Title of paper. In Editor’s First initial. Last name (Ed.), Title of book (page range). Publisher.

Example: Johnson, R. (2015). The effects of climate change on agriculture. In S. Lee (Ed.), Climate Change and Sustainable Development (pp. 45-62). Springer.

Format: Author’s Last name, First initial. (Year, Month Day of publication). Title of page. Website name. URL.

Example: Smith, J. (2017, May 23). The history of the internet. Encyclopedia Britannica. https://www.britannica.com/topic/history-of-the-internet

News article:

Format: Author’s Last name, First initial. (Year, Month Day of publication). Title of article. Title of newspaper, page number (if applicable).

Example: Thompson, E. (2022, January 5). New study finds coffee may lower risk of dementia. The New York Times, A1.

IEEE Format

Author(s). (Year of Publication). Title of Book. Publisher.

Smith, J. K. (2015). The Power of Habit: Why We Do What We Do in Life and Business. Random House.

Journal Article:

Author(s). (Year of Publication). Title of Article. Title of Journal, Volume Number (Issue Number), page numbers.

Johnson, T. J., & Kaye, B. K. (2016). Interactivity and the Future of Journalism. Journalism Studies, 17(2), 228-246.

Author(s). (Year of Publication). Title of Paper. Paper presented at Conference Name, Location.

Jones, L. K., & Brown, M. A. (2018). The Role of Social Media in Political Campaigns. Paper presented at the 2018 International Conference on Social Media and Society, Copenhagen, Denmark.

  • Website: Author(s) or Organization Name. (Year of Publication or Last Update). Title of Webpage. Website Name. URL.

Example: National Aeronautics and Space Administration. (2019, August 29). NASA’s Mission to Mars. NASA. https://www.nasa.gov/topics/journeytomars/index.html

  • News Article: Author(s). (Year of Publication). Title of Article. Name of News Source. URL.

Example: Johnson, M. (2022, February 16). Climate Change: Is it Too Late to Save the Planet? CNN. https://www.cnn.com/2022/02/16/world/climate-change-planet-scn/index.html

Vancouver Style

In-text citation: Use superscript numbers to cite sources in the text, e.g., “The study conducted by Smith and Johnson^1 found that…”.

Reference list citation: Format: Author(s). Title of book. Edition if any. Place of publication: Publisher; Year of publication.

Example: Smith J, Johnson L. Introduction to Molecular Biology. 2nd ed. New York: Wiley-Blackwell; 2015.

In-text citation: Use superscript numbers to cite sources in the text, e.g., “Several studies have reported that^1,2,3…”.

Reference list citation: Format: Author(s). Title of article. Abbreviated name of journal. Year of publication; Volume number (Issue number): Page range.

Example: Jones S, Patel K, Smith J. The effects of exercise on cardiovascular health. J Cardiol. 2018; 25(2): 78-84.

In-text citation: Use superscript numbers to cite sources in the text, e.g., “Previous research has shown that^1,2,3…”.

Reference list citation: Format: Author(s). Title of paper. In: Editor(s). Title of the conference proceedings. Place of publication: Publisher; Year of publication. Page range.

Example: Johnson L, Smith J. The role of stem cells in tissue regeneration. In: Patel S, ed. Proceedings of the 5th International Conference on Regenerative Medicine. London: Academic Press; 2016. p. 68-73.

In-text citation: Use superscript numbers to cite sources in the text, e.g., “According to the World Health Organization^1…”.

Reference list citation: Format: Author(s). Title of webpage. Name of website. URL [Accessed Date].

Example: World Health Organization. Coronavirus disease (COVID-19) advice for the public. World Health Organization. https://www.who.int/emergencies/disease/novel-coronavirus-2019/advice-for-public [Accessed 3 March 2023].

In-text citation: Use superscript numbers to cite sources in the text, e.g., “According to the New York Times^1…”.

Reference list citation: Format: Author(s). Title of article. Name of newspaper. Year Month Day; Section (if any): Page number.

Example: Jones S. Study shows that sleep is essential for good health. The New York Times. 2022 Jan 12; Health: A8.

Author(s). Title of Book. Edition Number (if it is not the first edition). Publisher: Place of publication, Year of publication.

Example: Smith, J. Chemistry of Natural Products. 3rd ed.; CRC Press: Boca Raton, FL, 2015.

Journal articles:

Author(s). Article Title. Journal Name Year, Volume, Inclusive Pagination.

Example: Garcia, A. M.; Jones, B. A.; Smith, J. R. Selective Synthesis of Alkenes from Alkynes via Catalytic Hydrogenation. J. Am. Chem. Soc. 2019, 141, 10754-10759.

Research papers:

Author(s). Title of Paper. Journal Name Year, Volume, Inclusive Pagination.

Example: Brown, H. D.; Jackson, C. D.; Patel, S. D. A New Approach to Photovoltaic Solar Cells. J. Mater. Chem. 2018, 26, 134-142.

Author(s) (if available). Title of Webpage. Name of Website. URL (accessed Month Day, Year).

Example: National Institutes of Health. Heart Disease and Stroke. National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health-topics/heart-disease-and-stroke (accessed April 7, 2023).

News articles:

Author(s). Title of Article. Name of News Publication. Date of Publication. URL (accessed Month Day, Year).

Example: Friedman, T. L. The World is Flat. New York Times. April 7, 2023. https://www.nytimes.com/2023/04/07/opinion/world-flat-globalization.html (accessed April 7, 2023).

In AMA Style Format, the citation for a book should include the following information, in this order:

  • Title of book (in italics)
  • Edition (if applicable)
  • Place of publication
  • Year of publication

Lodish H, Berk A, Zipursky SL, et al. Molecular Cell Biology. 4th ed. New York, NY: W. H. Freeman; 2000.

In AMA Style Format, the citation for a journal article should include the following information, in this order:

  • Title of article
  • Abbreviated title of journal (in italics)
  • Year of publication; volume number(issue number):page numbers.

Chen H, Huang Y, Li Y, et al. Effects of mindfulness-based stress reduction on depression in adolescents and young adults: a systematic review and meta-analysis. JAMA Netw Open. 2020;3(6):e207081. doi:10.1001/jamanetworkopen.2020.7081

In AMA Style Format, the citation for a research paper should include the following information, in this order:

  • Title of paper
  • Name of journal or conference proceeding (in italics)
  • Volume number(issue number):page numbers.

Bredenoord AL, Kroes HY, Cuppen E, Parker M, van Delden JJ. Disclosure of individual genetic data to research participants: the debate reconsidered. Trends Genet. 2011;27(2):41-47. doi:10.1016/j.tig.2010.11.004

In AMA Style Format, the citation for a website should include the following information, in this order:

  • Title of web page or article
  • Name of website (in italics)
  • Date of publication or last update (if available)
  • URL (website address)
  • Date of access (month day, year)

Centers for Disease Control and Prevention. How to protect yourself and others. CDC. Published February 11, 2022. Accessed February 14, 2022. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html

In AMA Style Format, the citation for a news article should include the following information, in this order:

  • Name of newspaper or news website (in italics)
  • Date of publication

Gorman J. Scientists use stem cells from frogs to build first living robots. The New York Times. January 13, 2020. Accessed January 14, 2020. https://www.nytimes.com/2020/01/13/science/living-robots-xenobots.html

Bluebook Format

One author: Daniel J. Solove, The Future of Reputation: Gossip, Rumor, and Privacy on the Internet (Yale University Press 2007).

Two or more authors: Martha Nussbaum and Saul Levmore, eds., The Offensive Internet: Speech, Privacy, and Reputation (Harvard University Press 2010).

Journal article

One author: Daniel J. Solove, “A Taxonomy of Privacy,” University of Pennsylvania Law Review 154, no. 3 (January 2006): 477-560.

Two or more authors: Ethan Katsh and Andrea Schneider, “The Emergence of Online Dispute Resolution,” Journal of Dispute Resolution 2003, no. 1 (2003): 7-19.

One author: Daniel J. Solove, “A Taxonomy of Privacy,” GWU Law School Public Law Research Paper No. 113, 2005.

Two or more authors: Ethan Katsh and Andrea Schneider, “The Emergence of Online Dispute Resolution,” Cyberlaw Research Paper Series Paper No. 00-5, 2000.

WebsiteElectronic Frontier Foundation, “Surveillance Self-Defense,” accessed April 8, 2023, https://ssd.eff.org/.

News article

One author: Mark Sherman, “Court Deals Major Blow to Net Neutrality Rules,” ABC News, January 14, 2014, https://abcnews.go.com/Politics/wireStory/court-deals-major-blow-net-neutrality-rules-21586820.

Two or more authors: Siobhan Hughes and Brent Kendall, “AT&T Wins Approval to Buy Time Warner,” Wall Street Journal, June 12, 2018, https://www.wsj.com/articles/at-t-wins-approval-to-buy-time-warner-1528847249.

In-Text Citation: (Author’s last name Year of Publication: Page Number)

Example: (Smith 2010: 35)

Reference List Citation: Author’s last name First Initial. Title of Book. Edition. Place of publication: Publisher; Year of publication.

Example: Smith J. Biology: A Textbook. 2nd ed. New York: Oxford University Press; 2010.

Example: (Johnson 2014: 27)

Reference List Citation: Author’s last name First Initial. Title of Article. Abbreviated Title of Journal. Year of publication;Volume(Issue):Page Numbers.

Example: Johnson S. The role of dopamine in addiction. J Neurosci. 2014;34(8): 2262-2272.

Example: (Brown 2018: 10)

Reference List Citation: Author’s last name First Initial. Title of Paper. Paper presented at: Name of Conference; Date of Conference; Place of Conference.

Example: Brown R. The impact of social media on mental health. Paper presented at: Annual Meeting of the American Psychological Association; August 2018; San Francisco, CA.

Example: (World Health Organization 2020: para. 2)

Reference List Citation: Author’s last name First Initial. Title of Webpage. Name of Website. URL. Published date. Accessed date.

Example: World Health Organization. Coronavirus disease (COVID-19) pandemic. WHO website. https://www.who.int/emergencies/disease-coronavirus-2019. Updated August 17, 2020. Accessed September 5, 2021.

Example: (Smith 2019: para. 5)

Reference List Citation: Author’s last name First Initial. Title of Article. Title of Newspaper or Magazine. Year of publication; Month Day:Page Numbers.

Example: Smith K. New study finds link between exercise and mental health. The New York Times. 2019;May 20: A6.

Purpose of Research Paper Citation

The purpose of citing sources in a research paper is to give credit to the original authors and acknowledge their contribution to your work. By citing sources, you are also demonstrating the validity and reliability of your research by showing that you have consulted credible and authoritative sources. Citations help readers to locate the original sources that you have referenced and to verify the accuracy and credibility of your research. Additionally, citing sources is important for avoiding plagiarism, which is the act of presenting someone else’s work as your own. Proper citation also shows that you have conducted a thorough literature review and have used the existing research to inform your own work. Overall, citing sources is an essential aspect of academic writing and is necessary for building credibility, demonstrating research skills, and avoiding plagiarism.

Advantages of Research Paper Citation

There are several advantages of research paper citation, including:

  • Giving credit: By citing the works of other researchers in your field, you are acknowledging their contribution and giving credit where it is due.
  • Strengthening your argument: Citing relevant and reliable sources in your research paper can strengthen your argument and increase its credibility. It shows that you have done your due diligence and considered various perspectives before drawing your conclusions.
  • Demonstrating familiarity with the literature : By citing various sources, you are demonstrating your familiarity with the existing literature in your field. This is important as it shows that you are well-informed about the topic and have done a thorough review of the available research.
  • Providing a roadmap for further research: By citing relevant sources, you are providing a roadmap for further research on the topic. This can be helpful for future researchers who are interested in exploring the same or related issues.
  • Building your own reputation: By citing the works of established researchers in your field, you can build your own reputation as a knowledgeable and informed scholar. This can be particularly helpful if you are early in your career and looking to establish yourself as an expert in your field.

About the author

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Muhammad Hassan

Researcher, Academic Writer, Web developer

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CINAHL has a built-in citation generator!

View the full article description by clicking on the title of the article in your results list. Then use the citation tools on the right-hand side of the page:

  • Cite will display the article's citation in a variety of different citation formats. Scroll down a bit to see the APA citation (7th ed.)
  • Email opens a form where you can enter your own email address. Use the drop-down menu on the form to select APA.

Remember: Online citation generators aren't perfect! They make formatting citations easier than starting from scratch. But you should ALWAYS check the citation and correct any errors. YOU are ultimately responsible for your citations!

  • 7th Edition APA Style Quick Reference Guide
  • APA Formatting & Style Guide - 7th edition Online Writing Lab at Purdue University (OWL)
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  • APA Sample Paper An example of a paper written in APA style.
  • Zbib Citation Generator Be sure to select APA style from the drop-down menu under "Bibliography."

Websites and webpages are often difficult to cite! Follow these steps to do the best you can:

  • Copy and paste the URL into Zbib .
  • Webpage on a website
  • Whole website references

Definition of Plagiarism :

"Stealing and/or using the ideas or writings of another in a paper or report and claiming them as your own.  This includes but is not limited to the use, by paraphrase or direct quotation, of the work of another person without full and clear acknowledgement."  - CSU Code of Student Conduct

Write and cite responsibly!

  • Cite your source for any idea that is not common knowledge.
  • Paraphrasing means integrating your research into your writing. Read thoroughly and filter information through your own understanding. Put it into your own words and include a citation to acknowledge your source.
  • Put quotation marks around direct quotes. 
  • Need help? Check out the citation style guides on this page or make an appointment with the Writing Center at 216-687-6981 .

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  • Engaging With Sources Effectively

by acburton | Apr 30, 2024 | Resources for Students , Writing Resources

We’ve talked about the three ways to integrate sources effectively that allow writers to provide evidence and support for their argument, enter the scholarly conversation, and give credit to the original authors of the work that has helped and informed them. Sources also encourage writers to share their own knowledge and authority with others, help readers find additional sources related to the topic they are interested in, and protect you by giving credit where credit is due (thus avoiding plagiarism). In other words, sources are much more than just something we add on at the end of our writing!

When writing about a source or simply referencing it, we are positioning ourselves in response to, or in conversation with that source, with the goal of focusing our writing on our own argument/thesis. Sources do not stand on their own within a piece of writing and that is why, alongside finding strong and reputable sources worth responding to and making sure that we fully understand sources (even before writing about them), it is critical to engage with our sources in meaningful ways. But how exactly do we effectively engage with our sources in our writing?

Joseph Harris, in How To Do Things with Texts , presents four different ways of “rewriting the work of others”, three of which provide insight into the how of engaging sources. When a writer forwards the work of another writer, they are applying the concepts, topics, or terms from one reading, text, or situation to a different reading, text or situation. By countering the ideas found in source material, a writer argues “against the grain of a text” by underlining and countering ideas that a writer may be in disagreement with. Taking an approach is the adaptation of a theory or method from one writer to a new set of issues or texts. Harris’ book provides a thorough classification of methods to engage with a source. For something a little simpler, here are three basic ways you can get started effectively engaging with sources (Harris 5-7).

3 Basic Ways to Engage with Sources Effectively

  • Disagree and Explain Why. Persuade your reader that the argument or information in a source should be questioned or challenged.
  • Agree, But With Your Own Take. Add something new to the conversation. Expand a source’s insights or argument to a new situation or your own example. Provide new evidence and discuss new implications.
  • Agree and Disagree Simultaneously. This is a nuanced approach to complex sources or complex topics. You can, for example, agree with a source’s overall thesis, but disagree with some of its reasoning or evidence.

Remember that this is not an exhaustive list. When engaging with others’ sources as a way to support our own ideas and argument, it is crucial that we engage with critical thinking, nuance, and objectivity to ensure that we are constructing unbiased, thoughtful, and compelling arguments.

Some of the different areas throughout your essay that will benefit from effective engagement with source material include: your thesis statement, analysis, and conclusion.

  • Thesis Statement. The argument that you make in your thesis statement can challenge, weaken, support, or strengthen what is being argued by your source or sources.

Analysis. Thorough analysis in your body paragraphs emphasize the role of your argument in comparison to that found in your source material. Bring your analysis back to your thesis statement to reinforce the connection between the two.

  • Conclusion. Consider the “big picture” or “takeaways” to leave your reader with.

There are many other, sometimes optional, essay sections or writing styles that benefit from critical engagement with a source. These can include literature reviews, reflections, critiques, and so on.

Strategies for Engaging Critically From Start to Finish

  • Aim to dig deeper than surface level. Ask the ‘how’ and ‘why’ of a source, as well as ‘how’ and ‘why’ it is relevant to the topic at hand and the argument you are making.
  • Ask yourself if you’ve addressed every possible question, concern, critique, or “what if” that comes to mind; put yourself in the place of your readers.
  • Use TEAL body paragraph development as a template and guide for developing thorough analysis in your body paragraphs. Effectively engaging with your sources is essential to the analysis portion of the TEAL formula and to creating meaningful engagement with your sources.
  • Visit the Writing Center for additional support on crafting engaging analyses and for other ways to engage with your source material from thesis to conclusion.

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Research: Where to Begin

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Research isn't something that only scientists and professors do. Any time you use sources to investigate claims or reach new conclusions, you are performing research. Research happens in virtually all fields, so it’s vitally important to know how to conduct research and navigate through source material regardless of your professional or academic role.

Choosing and Narrowing Your Research Topic

Before beginning the process of looking for sources, it’s important to choose a research topic that is specific enough to explore in-depth. If your focus is too broad, it will be difficult to find sources that back up what you’re trying to say.

If your instructor gives you the flexibility to choose your own research topic, you might begin by brainstorming  a list of topics that interest you ( click here to visit an OWL page that can help you get started brainstorming or prewriting ). Once you find something that grabs your attention, the next step is to narrow your topic to a manageable scope. Some ways to narrow your focus are by sub-topic, demographic, or time period.

For example, suppose that you want to research cancer treatments. Cancer treatment is a fairly broad topic, so you would be wise to at least consider narrowing your scope. For example, you could focus on a sub-topic of cancer treatment, such as chemotherapy or radiation therapy. However, these are still broad topics, so you might also narrow your topic to a narrower sub-topic or even examine how these topics relate to a specific demographic or time period. In the end, you might decide to research how radiation therapy for women over fifty has changed in the past twenty years. In sum, having a specific idea of what you want to research helps you find a topic that feels more manageable.

Writing Your Research Question

Writing your research topic as a question helps you focus your topic in a clear and concise way. It ensure that your topic is arguable. While not all research papers have to offer an explicit argument, many do.

For the above example, you might phrase your research question like this: "How has radiation therapy changed in the past twenty years for women over fifty?" Of course, phrasing this topic as a question assumes that the research has, in fact, changed. Reading your sources (or, to begin with, at least summaries and abstracts of those sources) will help you formulate a research question that makes sense.

Knowing What Types of Sources You Need

Depending on the type of research you’re doing, you may need to use different types of sources. Research is usually divided into scholarly and popular, and primary and secondary. For more information on specific details about these types of sources, visit our "Where to Begin" page in our "Evaluating Sources" subsection.  This subsection contains additional pages that explore various kinds of sources (like, e.g., internet sources) in more detail.

Asking Productive Questions

Before you begin your research, you should ask yourself questions that help narrow your search parameters.

What kind of information are you looking for?

Different types of research will require different sources. It’s important to know what kinds of sources your research demands. Ask whether you need facts or opinions, news reports, research studies, statistics and data, personal reflections, archival research, etc. Restricting yourself to only the most relevant kinds of sources will make the research process seem less daunting.

Where do you need to look for your research?

Your research topic will also dictate where you find your sources. This extends beyond simply whether you use the internet or a print source. For example, if you are searching for information on a current event, a well-regarded newspaper like the  New York Times  or  Wall Street Journal  could  be a useful source. If you are searching for statistics on some aspect of the U.S. population, then you might want to start with government documents, such as census reports. While much high-level academic research relies mainly on the sorts of academic journal articles and scholarly books that can be found in university libraries, depending the nature of your research project, you may need to look elsewhere.

How much information do you need?

Different research projects require different numbers of sources. For example, if you need to address both sides of a controversial issue, you may need to find more sources than if you were pursuing a non-controversial topic. Be sure to speak with your instructor if you are unclear on how many sources you will be expected to use.

How timely does your research need to be?

Depending on your research topic, the timeliness of your source may or may not matter. For example, if you are looking into recent changes in a specific scientific field, you would want the most up-to-date research. However, if you were researching the War of 1812, you might benefit from finding primary sources written during that time period.

U.S. Constitution.net

U.S. Constitution.net

How to cite this site – the u.s. constitution online – usconstitution.net, how to cite this site.

Jump to: Citing the Constitution

It is very important when writing a paper for a school project (at any level, from elementary school to graduate school) to properly cite your sources. Where did you find your information? Citations are placed in the text as footnotes or endnotes, and/or placed at the end of your work in a bibliography. This page will handle a few different possibilities. The first is to answer the question “How do I cite a page on this site?” or, as I like to say, “How to cite the site.”

There are two main areas that someone might wish to cite on this site. The first is one of the pages found on the site. Several are simply electronic copies of historical documents, while others are research pages or opinion pages. You should be able to discern which is which pretty easily. Unless the information is a copy of a historical document, and unless otherwise noted, everything here is written by the Webmaster, Steve Mount.

Here is a standard way to cite an HTML page published on the Internet, according to the Columbia Guide to Online Style :

  • Mount, Steve. “Constitutional Topic: Martial Law.” USConstitution.net. 30 Nov 2001. http://www.usconstitution.net/consttop_mlaw.html (3 Dec 2001)

Specifically, the data is as follows: Author, Title, Site, Modification Date (found at the bottom of every page), URL, and the date the page was accessed. The two dates are critical because of the changeable nature of the Web.

The next citation uses the APA format. This standard comes from the American Psychological Association, and is often used in psychology and other social sciences:

  • Mount, S. (2010). Constitutional topic: due process. Retrieved February 23, 2011 from http://www.usconstitution.net/consttop_duep.html

Specifically, the data is as follows: Author, Modification Year (found at the bottom of every page), page title, the date the page was accessed, and the URL.

Finally, the MLA style is often used. This style comes from The Modern Language Association. With this style, citations are noted in the text and full references are given in a Works Cited list at the end of the paper.

  • Inline: (Mount)
  • Works Cited: Mount, Steve. “Constitutional Topic: The Census.” USConstitution.net . 3 Jan. 2011. 27 Feb. 2011 .

Specifically, the data is as follows: Author, Title, Site, Modification Date, thee date the page was accessed, and URL.

The second source of information is this site’s Message Boards. The primary information available in the Message Boards is opinion. Because the opinions are those of the posters, the citation of a message needs to include the name or handle of the poster. Here is an example, in the Columbia Style, for a posting from the Classic Boards on this site:

  • Ian. “Re: Question regarding Law.” 2 Dec 2001. USConstitution.net Q&A Board. http://www.usconstitution.net/cgi-bin/wwwbmsg.cgi?const&001280.wwb (3 Dec 2001)

The data is as follows: Poster, Subject, Date Posted, Board Name, URL, and date accessed.

All posts created after November 2003 used the new messaging software. Here is an example for a posting using the new software:

  • Andy. “Re: Impeach Scalia?” 5 Feb 2004. Debate Archives. http://www.usconstitution.net/yabb/YaBB.cgi?board=debarch;action=display;num=1077548457 (25 Feb 2004)

Citing the U.S. Constitution

Another common question involves how to cite the Constitution itself. There are two forms, a long form and a short form. In a legal document, the short form will suffice in all instances, whereas in a non-legal paper, the long form should be used once, and the short form can be used thereafter.

  • “The Constitution of the United States,” Article 1, Section 8, Clause 5.
  • “The Constitution of the United States,” Amendment 5.

Short Form:

  • U.S. Const. art. I, § 8, cl. 5.
  • U.S. Const. am. 5.

In place of the “§” symbol, the abbreviation “sect.” can be used. In a paper dealing primarily with the Constitution, there is no need to mention “U.S. Const.”

Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.

Volume 30, Number 7—July 2024

Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus Infection in Domestic Dairy Cattle and Cats, United States, 2024

Suggested citation for this article

We report highly pathogenic avian influenza A(H5N1) virus in dairy cattle and cats in Kansas and Texas, United States, which reflects the continued spread of clade 2.3.4.4b viruses that entered the country in late 2021. Infected cattle experienced nonspecific illness, reduced feed intake and rumination, and an abrupt drop in milk production, but fatal systemic influenza infection developed in domestic cats fed raw (unpasteurized) colostrum and milk from affected cows. Cow-to-cow transmission appears to have occurred because infections were observed in cattle on Michigan, Idaho, and Ohio farms where avian influenza virus–infected cows were transported. Although the US Food and Drug Administration has indicated the commercial milk supply remains safe, the detection of influenza virus in unpasteurized bovine milk is a concern because of potential cross-species transmission. Continued surveillance of highly pathogenic avian influenza viruses in domestic production animals is needed to prevent cross-species and mammal-to-mammal transmission.

Highly pathogenic avian influenza (HPAI) viruses pose a threat to wild birds and poultry globally, and HPAI H5N1 viruses are of even greater concern because of their frequent spillover into mammals. In late 2021, the Eurasian strain of H5N1 (clade 2.3.4.4b) was detected in North America ( 1 , 2 ) and initiated an outbreak that continued into 2024. Spillover detections and deaths from this clade have been reported in both terrestrial and marine mammals in the United States ( 3 , 4 ). The detection of HPAI H5N1 clade 2.3.4.4b virus in severe cases of human disease in Ecuador ( 5 ) and Chile ( 6 ) raises further concerns regarding the pandemic potential of specific HPAI viruses.

In February 2024, veterinarians were alerted to a syndrome occurring in lactating dairy cattle in the panhandle region of northern Texas. Nonspecific illness accompanied by reduced feed intake and rumination and an abrupt drop in milk production developed in affected animals. The milk from most affected cows had a thickened, creamy yellow appearance similar to colostrum. On affected farms, incidence appeared to peak 4–6 days after the first animals were affected and then tapered off within 10–14 days; afterward, most animals were slowly returned to regular milking. Clinical signs were commonly reported in multiparous cows during middle to late lactation; ≈10%–15% illness and minimal death of cattle were observed on affected farms. Initial submissions of blood, urine, feces, milk, and nasal swab samples and postmortem tissues to regional diagnostic laboratories did not reveal a consistent, specific cause for reduced milk production. Milk cultures were often negative, and serum chemistry testing showed mildly increased aspartate aminotransferase, gamma-glutamyl transferase, creatinine kinase, and bilirubin values, whereas complete blood counts showed variable anemia and leukocytopenia.

In early March 2024, similar clinical cases were reported in dairy cattle in southwestern Kansas and northeastern New Mexico; deaths of wild birds and domestic cats were also observed within affected sites in the Texas panhandle. In > 1 dairy farms in Texas, deaths occurred in domestic cats fed raw colostrum and milk from sick cows that were in the hospital parlor. Antemortem clinical signs in affected cats were depressed mental state, stiff body movements, ataxia, blindness, circling, and copious oculonasal discharge. Neurologic exams of affected cats revealed the absence of menace reflexes and pupillary light responses with a weak blink response.

On March 21, 2024, milk, serum, and fresh and fixed tissue samples from cattle located in affected dairies in Texas and 2 deceased cats from an affected Texas dairy farm were received at the Iowa State University Veterinary Diagnostic Laboratory (ISUVDL; Ames, IA, USA). The next day, similar sets of samples were received from cattle located in affected dairies in Kansas. Milk and tissue samples from cattle and tissue samples from the cats tested positive for influenza A virus (IAV) by screening PCR, which was confirmed and characterized as HPAI H5N1 virus by the US Department of Agriculture National Veterinary Services Laboratory. Detection led to an initial press release by the US Department of Agriculture Animal and Plant Health Inspection Service on March 25, 2024, confirming HPAI virus in dairy cattle ( 7 ). We report the characterizations performed at the ISUVDL for HPAI H5N1 viruses infecting cattle and cats in Kansas and Texas.

Materials and Methods

Milk samples (cases 2–5) and fresh and formalin-fixed tissues (cases 1, 3–5) from dairy cattle were received at the ISUVDL from Texas on March 21 and from Kansas on March 22, 2024. The cattle exhibited nonspecific illness and reduced lactation, as described previously. The tissue samples for diagnostic testing came from 3 cows that were euthanized and 3 that died naturally; all postmortem examinations were performed on the premises of affected farms.

The bodies of 2 adult domestic shorthaired cats from a north Texas dairy farm were received at the ISUVDL for a complete postmortem examination on March 21, 2024. The cats were found dead with no apparent signs of injury and were from a resident population of ≈24 domestic cats that had been fed milk from sick cows. Clinical disease in cows on that farm was first noted on March 16; the cats became sick on March 17, and several cats died in a cluster during March 19–20. In total, >50% of the cats at that dairy became ill and died. We collected cerebrum, cerebellum, eye, lung, heart, spleen, liver, lymph node, and kidney tissue samples from the cats and placed them in 10% neutral-buffered formalin for histopathology.

At ISUVDL, we trimmed, embedded in paraffin, and processed formalin-fixed tissues from affected cattle and cats for hematoxylin/eosin staining and histologic evaluation. For immunohistochemistry (IHC), we prepared 4-µm–thick sections from paraffin-embedded tissues, placed them on Superfrost Plus slides (VWR, https://www.vwr.com ), and dried them for 20 minutes at 60°C. We used a Ventana Discovery Ultra IHC/ISH research platform (Roche, https://www.roche.com ) for deparaffinization until and including counterstaining. We obtained all products except the primary antibody from Roche. Automated deparaffination was followed by enzymatic digestion with protease 1 for 8 minutes at 37°C and endogenous peroxidase blocking. We obtained the primary influenza A virus antibody from the hybridoma cell line H16-L10–4R5 (ATCC, https://www.atcc.org ) and diluted at 1:100 in Discovery PSS diluent; we incubated sections with antibody for 32 minutes at room temperature. Next, we incubated the sections with a hapten-labeled conjugate, Discovery anti-mouse HQ, for 16 minutes at 37°C followed by a 16-minute incubation with the horse radish peroxidase conjugate, Discovery anti-HQ HRP. We used a ChromoMap DAB kit for antigen visualization, followed by counterstaining with hematoxylin and then bluing. Positive controls were sections of IAV-positive swine lung. Negative controls were sections of brain, lung, and eyes from cats not infected with IAV.

We diluted milk samples 1:3 vol/vol in phosphate buffered saline, pH 7.4 (Gibco/Thermo Fisher Scientific, https://www.thermofisher.com ) by mixing 1 unit volume of milk and 3 unit volumes of phosphate buffered saline. We prepared 10% homogenates of mammary glands, brains, lungs, spleens, and lymph nodes in Earle’s balanced salt solution (Sigma-Aldrich, https://www.sigmaaldrich.com ). Processing was not necessary for ocular fluid, rumen content, or serum samples. After processing, we extracted samples according to a National Animal Health Laboratory Network (NAHLN) protocol that had 2 NAHLN-approved deviations for ISUVDL consisting of the MagMax Viral RNA Isolation Kit for 100 µL sample volumes and a Kingfisher Flex instrument (both Thermo Fisher Scientific).

We performed real-time reverse transcription PCR (rRT-PCR) by using an NAHLN-approved assay with 1 deviation, which was the VetMAX-Gold SIV Detection kit (Thermo Fisher Scientific), to screen for the presence of IAV RNA. We tested samples along with the VetMAX XENO Internal Positive Control to monitor the possible presence of PCR inhibitors. Each rRT-PCR 96-well plate had 2 positive amplification controls, 2 negative amplification controls, 1 positive extraction control, and 1 negative extraction control. We ran the rRT-PCR on an ABI 7500 Fast thermocycler and analyzed data with Design and Analysis Software 2.7.0 (both Thermo Fisher Scientific). We considered samples with cycle threshold (Ct) values <40.0 to be positive for virus.

After the screening rRT-PCR, we analyzed IAV RNA–positive samples for the H5 subtype and H5 clade 2.3.4.4b by using the same RNA extraction and NAHLN-approved rRT-PCR protocols as described previously, according to standard operating procedures. We performed PCR on the ABI 7500 Fast thermocycler by using appropriate controls to detect H5-specific IAV. We considered samples with Ct values <40.0 to be positive for the IAV H5 subtype.

We conducted genomic sequencing of 2 milk samples from infected dairy cattle from Texas and 2 tissue samples (lung and brain) from cats that died at a different Texas dairy. We subjected the whole-genome sequencing data to bioinformatics analysis to assemble the 8 different IAV segment sequences according to previously described methods ( 8 ). We used the hemagglutinin (HA) and neuraminidase (NA) sequences for phylogenetic analysis. We obtained reference sequences for the HA and NA segments of IAV H5 clade 2.3.4.4 from publicly available databases, including GISAID ( https://www.gisaid.org ) and GenBank. We aligned the sequences by using MAFFT version 7.520 software ( https://mafft.cbrc.jp/alignment/server/index.html ) to create multiple sequence alignments for subsequent phylogenetic analysis. We used IQTree2 ( https://github.com/iqtree/iqtree2 ) to construct the phylogenetic tree from the aligned sequences. The software was configured to automatically identify the optimal substitution model by using the ModelFinder Plus option, ensuring the selection of the most suitable model for the dataset and, thereby, improving the accuracy of the reconstructed tree. We visualized the resulting phylogenetic tree by using iTOL ( https://itol.embl.de ), a web-based platform for interactive tree exploration and annotation.

Gross Lesions in Cows and Cats

All cows were in good body condition with adequate rumen fill and no external indications of disease. Postmortem examinations of the affected dairy cows revealed firm mammary glands typical of mastitis; however, mammary gland lesions were not consistent. Two cows that were acutely ill before postmortem examination had grossly normal milk and no abnormal mammary gland lesions. The gastrointestinal tract of some cows had small abomasal ulcers and shallow linear erosions of the intestines, but those observations were also not consistent in all animals. The colon contents were brown and sticky, suggesting moderate dehydration. The feces contained feed particles that appeared to have undergone minimal ruminal fermentation. The rumen contents had normal color and appearance but appeared to have undergone minimal fermentation.

The 2 adult cats (1 intact male, 1 intact female) received at the ISUVDL were in adequate body and postmortem condition. External examination was unremarkable. Mild hemorrhages were observed in the subcutaneous tissues over the dorsal skull, and multifocal meningeal hemorrhages were observed in the cerebrums of both cats. The gastrointestinal tracts were empty, and no other gross lesions were observed.

Microscopic Lesions in Cows and Cats

Mammary gland lesions in cattle in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. A, B) Mammary gland tissue sections stained with hematoxylin and eosin. A) Arrowheads indicate segmental loss within open secretory mammary alveoli. Original magnification ×40. B) Arrowheads indicate epithelial degeneration and necrosis lining alveoli with intraluminal sloughing. Asterisk indicates intraluminal neutrophilic inflammation. Original magnification ×400. C, D) Mammary gland tissue sections stained by using avian influenza A immunohistochemistry. C) Brown staining indicates lobular distribution of avian influenza A virus. Original magnification ×40. D) Brown staining indicates strong nuclear and intracytoplasmic immunoreactivity of intact and sloughed epithelial cells within mammary alveoli. Original magnification ×400.

Figure 1 . Mammary gland lesions in cattle in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. A, B) Mammary gland...

The chief microscopic lesion observed in affected cows was moderate acute multifocal neutrophilic mastitis ( Figure 1 ); however, mammary glands were not received from every cow. Three cows had mild neutrophilic or lymphocytic hepatitis. Because they were adult cattle, other observed microscopic lesions (e.g., mild lymphoplasmacytic interstitial nephritis and mild to moderate lymphocytic abomasitis) were presumed to be nonspecific, age-related changes. We did not observe major lesions in the other evaluated tissues. We performed IHC for IAV antigen on all evaluated tissues; the only tissues with positive immunoreactivity were mastitic mammary glands from 2 cows that showed nuclear and cytoplasmic labeling of alveolar epithelial cells and cells within lumina ( Figure 1 ) and multifocal germinal centers within a lymph node from 1 cow ( Table 1 ).

Lesions in cat tissues in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Tissue sections were stained with hematoxylin and eosin; insets show brown staining of avian influenza A viruses via immunohistochemistry by using the chromogen 3,3′-diaminobenzidine tetrahydrochloride. Original magnification ×200 for all images and insets. A) Section from cerebral tissue. Arrowheads show perivascular lymphocytic encephalitis, gliosis, and neuronal necrosis. Inset shows neurons. B) Section of lung tissue showing lymphocytic and fibrinous interstitial pneumonia with septal necrosis and alveolar edema; arrowheads indicate lymphocytes. Inset shows bronchiolar epithelium, necrotic cells, and intraseptal mononuclear cells. C) Section of heart tissue. Arrowhead shows interstitial lymphocytic myocarditis and focal peracute myocardial coagulative necrosis. Inset shows cardiomyocytes. D) Section of retinal tissue. Arrowheads show perivascular lymphocytic retinitis with segmental neuronal loss and rarefaction in the ganglion cell layer. Asterisks indicate attenuation of the inner plexiform and nuclear layers with artifactual retinal detachment. Insets shows all layers of the retina segmentally within affected areas have strong cytoplasmic and nuclear immunoreactivity to influenza A virus.

Figure 2 . Lesions in cat tissues in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Tissue sections were stained with...

Both cats had microscopic lesions consistent with severe systemic virus infection, including severe subacute multifocal necrotizing and lymphocytic meningoencephalitis with vasculitis and neuronal necrosis, moderate subacute multifocal necrotizing and lymphocytic interstitial pneumonia, moderate to severe subacute multifocal necrotizing and lymphohistiocytic myocarditis, and moderate subacute multifocal lymphoplasmacytic chorioretinitis with ganglion cell necrosis and attenuation of the internal plexiform and nuclear layers ( Table 2 ; Figure 2 ). We performed IHC for IAV antigen on multiple tissues (brain, eye, lung, heart, spleen, liver, and kidney). We detected positive IAV immunoreactivity in brain (intracytoplasmic, intranuclear, and axonal immunolabeling of neurons), lung, and heart, and multifocal and segmental immunoreactivity within all layers of the retina ( Figure 2 ).

PCR Data from Cows and Cats

We tested various samples from 8 clinically affected mature dairy cows by IAV screening and H5 subtype-specific PCR ( Table 3 ). Milk and mammary gland homogenates consistently showed low Ct values: 12.3–16.9 by IAV screening PCR, 17.6–23.1 by H5 subtype PCR, and 14.7–20.0 by H5 2.3.4.4 clade PCR (case 1, cow 1; case 2, cows 1 and 2; case 3, cow 1; and case 4, cow 1). We forwarded the samples to the National Veterinary Services Laboratory, which confirmed the virus was an HPAI H5N1 virus strain.

When available, we also tested tissue homogenates (e.g., lung, spleen, and lymph nodes), ocular fluid, and rumen contents from 6 cows by IAV and H5 subtype-specific PCR ( Table 3 ). However, the PCR findings were not consistent. For example, the tissue homogenates and ocular fluid tested positive in some but not all cows. In case 5, cow 1, the milk sample tested negative by IAV screening PCR, but the spleen homogenate tested positive by IAV screening, H5 subtype, and H5 2.3.4.4 PCR. For 2 cows (case 3, cow 1; and case 4, cow 1) that had both milk and rumen contents available, both samples tested positive for IAV. Nevertheless, all IAV-positive nonmammary gland tissue homogenates, ocular fluid, and rumen contents had markedly elevated Ct values in contrast to the low Ct values for milk and mammary gland homogenate samples.

We tested brain and lung samples from the 2 cats (case 6, cats 1 and 2) by IAV screening and H5 subtype-specific PCR ( Table 3 ). Both sample types were positive by IAV screening PCR; Ct values were 9.9–13.5 for brain and 17.4–24.4 for lung samples, indicating high amounts of virus nucleic acid in those samples. The H5 subtype and H5 2.3.4.4 PCR results were also positive for the brain and lung samples; Ct values were consistent with the IAV screening PCR ( Table 3 ).

Phylogenetic Analyses

We assembled the sequences of all 8 segments of the HPAI viruses from both cow milk and cat tissue samples. We used the hemagglutinin (HA) and neuraminidase (NA) sequences specifically for phylogenetic analysis to delineate the clade of the HA gene and subtype of the NA gene.

Phylogenetic analysis of hemagglutinin gene sequences in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Colors indicate different clades. Red text indicates the virus gene sequences from bovine milk and cats described in this report, confirming those viruses are highly similar and belong to H5 clade 2.3.4.4b. The hemagglutinin sequences from this report are most closely related to A/avian/Guanajuato/CENAPA-18539/2023|EPI_ISL_18755544|A_/_H5 (GISAID, https://www.gisaid.org) and have 99.66%–99.72% nucleotide identities.

Figure 3 . Phylogenetic analysis of hemagglutinin gene sequences in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Colors indicate different...

For HA gene analysis, both HA sequences derived from cow milk samples exhibited a high degree of similarity, sharing 99.88% nucleotide identity, whereas the 2 HA sequences from cat tissue samples showed complete identity at 100%. The HA sequences from the milk samples had 99.94% nucleotide identities with HA sequences from the cat tissues, resulting in a distinct subcluster comprising all 4 HA sequences, which clustered together with other H5N1 viruses belonging to clade 2.3.4.4b ( Figure 3 ). The HA sequences were deposited in GenBank (accession nos. PP599465 [case 2, cow 1], PP599473 [case 2, cow 2], PP692142 [case 6, cat 1], and PP692195 [case 6, cat 2]).

Phylogenetic analysis of neuraminidase gene sequences in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Colors indicate different subtypes. Red text indicates the virus gene sequences from bovine milk and cats described in this report, confirming those viruses belong to the N1 subtype. The neuraminidase sequences from this report had 99.52%–99.59% nucleotide identities to sequences from viruses isolated from a chicken and wild birds in 2023.

Figure 4 . Phylogenetic analysis of neuraminidase gene sequences in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Colors indicate different...

For NA gene analysis, the 2 NA sequences obtained from cow milk samples showed 99.93% nucleotide identity. Moreover, the NA sequences derived from the milk samples exhibited complete nucleotide identities (100%) with those from the cat tissues. The 4 NA sequences were grouped within the N1 subtype of HPAI viruses ( Figure 4 ). The NA sequences were deposited in GenBank (accession nos. PP599467 [case 2, cow 1], PP599475 [case 2, cow 2], PP692144 [case 6, cat 1], and PP692197 [case 6, cat 2]).

This case series differs from most previous reports of IAV infection in bovids, which indicated cattle were inapparently infected or resistant to infection ( 9 ). We describe an H5N1 strain of IAV in dairy cattle that resulted in apparent systemic illness, reduced milk production, and abundant virus shedding in milk. The magnitude of this finding is further emphasized by the high death rate (≈50%) of cats on farm premises that were fed raw colostrum and milk from affected cows; clinical disease and lesions developed that were consistent with previous reports of H5N1 infection in cats presumably derived from consuming infected wild birds ( 10 – 12 ). Although exposure to and consumption of dead wild birds cannot be completely ruled out for the cats described in this report, the known consumption of unpasteurized milk and colostrum from infected cows and the high amount of virus nucleic acid within the milk make milk and colostrum consumption a likely route of exposure. Therefore, our findings suggest cross-species mammal-to-mammal transmission of HPAI H5N1 virus and raise new concerns regarding the potential for virus spread within mammal populations. Horizontal transmission of HPAI H5N1 virus has been previously demonstrated in experimentally infected cats ( 13 ) and ferrets ( 14 ) and is suspected to account for large dieoffs observed during natural outbreaks in mink ( 15 ) and sea lions ( 16 ). Future experimental studies of HPAI H5N1 virus in dairy cattle should seek to confirm cross-species transmission to cats and potentially other mammals.

Clinical IAV infection in cattle has been infrequently reported in the published literature. The first report occurred in Japan in 1949, where a short course of disease with pyrexia, anorexia, nasal discharge, pneumonia, and decreased lactation developed in cattle ( 17 ). In 1997, a similar condition occurred in dairy cows in southwest England leading to a sporadic drop in milk production ( 18 ), and IAV seroconversion was later associated with reduced milk yield and respiratory disease ( 19 – 21 ). Rising antibody titers against human-origin influenza A viruses (H1N1 and H3N2) were later again reported in dairy cattle in England, which led to an acute fall in milk production during October 2005–March 2006 ( 22 ). Limited reports of IAV isolation from cattle exist; most reports occurred during the 1960s and 1970s in Hungary and in the former Soviet Union, where H3N2 was recovered from cattle experiencing respiratory disease ( 9 , 23 ). Direct detection of IAV in milk and the potential transmission from cattle to cats through feeding of unpasteurized milk has not been previously reported.

An IAV-associated drop in milk production in dairy cattle appears to have occurred during > 4 distinct periods and within 3 widely separated geographic areas: 1949 in Japan ( 17 ), 1997–1998 and 2005–2006 in Europe ( 19 , 21 ), and 2024 in the United States (this report). The sporadic occurrence of clinical disease in dairy cattle worldwide might be the result of changes in subclinical infection rates and the presence or absence of sufficient baseline IAV antibodies in cattle to prevent infection. Milk IgG, lactoferrin, and conglutinin have also been suggested as host factors that might reduce susceptibility of bovids to IAV infection ( 9 ). Contemporary estimates of the seroprevalence of IAV antibodies in US cattle are not well described in the published literature. One retrospective serologic survey in the United States in the late 1990s showed 27% of serum samples had positive antibody titers and 31% had low-positive titers for IAV H1 subtype-specific antigen in cattle with no evidence of clinical infections ( 24 ). Antibody titers for H5 subtype-specific antigen have not been reported in US cattle.

The susceptibility of domestic cats to HPAI H5N1 is well-documented globally ( 10 – 12 , 25 – 28 ), and infection often results in neurologic signs in affected felids and other terrestrial mammals ( 4 ). Most cases in cats result from consuming infected wild birds or contaminated poultry products ( 12 , 27 ). The incubation period in cats is short; clinical disease is often observed 2–3 days after infection ( 28 ). Brain tissue has been suggested as the best diagnostic sample to confirm HPAI virus infection in cats ( 10 ), and our results support that finding. One unique finding in the cats from this report is the presence of blindness and microscopic lesions of chorioretinitis. Those results suggest that further investigation into potential ocular manifestations of HPAI H5N1 virus infection in cats might be warranted.

The genomic sequencing and subsequent analysis of clinical samples from both bovine and feline sources provided considerable insights. The HA and NA sequences derived from both bovine milk and cat tissue samples from different Texas farms had a notable degree of similarity. Those findings strongly suggest a shared origin for the viruses detected in the dairy cattle and cat tissues. Further research, case series investigations, and surveillance data are needed to better understand and inform measures to curtail the clinical effects, shedding, and spread of HPAI viruses among mammals. Although pasteurization of commercial milk mitigates risks for transmission to humans, a 2019 US consumer study showed that 4.4% of adults consumed raw milk > 1 time during the previous year ( 29 ), indicating a need for public awareness of the potential presence of HPAI H5N1 viruses in raw milk.

Ingestion of feed contaminated with feces from wild birds infected with HPAI virus is presumed to be the most likely initial source of infection in the dairy farms. Although the exact source of the virus is unknown, migratory birds (Anseriformes and Charadriiformes) are likely sources because the Texas panhandle region lies in the Central Flyway, and those birds are the main natural reservoir for avian influenza viruses ( 30 ). HPAI H5N1 viruses are well adapted to domestic ducks and geese, and ducks appear to be a major reservoir ( 31 ); however, terns have also emerged as an important source of virus spread ( 32 ). The mode of transmission among infected cattle is also unknown; however, horizontal transmission has been suggested because disease developed in resident cattle herds in Michigan, Idaho, and Ohio farms that received infected cattle from the affected regions, and those cattle tested positive for HPAI H5N1 ( 33 ). Experimental studies are needed to decipher the transmission routes and pathogenesis (e.g., replication sites and movement) of the virus within infected cattle.

In conclusion, we showed that dairy cattle are susceptible to infection with HPAI H5N1 virus and can shed virus in milk and, therefore, might potentially transmit infection to other mammals via unpasteurized milk. A reduction in milk production and vague systemic illness were the most commonly reported clinical signs in affected cows, but neurologic signs and death rapidly developed in affected domestic cats. HPAI virus infection should be considered in dairy cattle when an unexpected and unexplained abrupt drop in feed intake and milk production occurs and for cats when rapid onset of neurologic signs and blindness develop. The recurring nature of global HPAI H5N1 virus outbreaks and detection of spillover events in a broad host range is concerning and suggests increasing virus adaptation in mammals. Surveillance of HPAI viruses in domestic production animals, including cattle, is needed to elucidate influenza virus evolution and ecology and prevent cross-species transmission.

Dr. Burrough is a professor and diagnostic pathologist at the Iowa State University College of Veterinary Medicine and Veterinary Diagnostic Laboratory. His research focuses on infectious diseases of livestock with an emphasis on swine.

Acknowledgment

We thank the faculty and staff at the ISUVDL who contributed to the processing and analysis of clinical samples in this investigation, the veterinarians involved with clinical assessments at affected dairies and various conference calls in the days before diagnostic submissions that ultimately led to the detection of HPAI virus in the cattle, and the US Department of Agriculture National Veterinary Services Laboratory and NAHLN for their roles and assistance in providing their expertise, confirmatory diagnostic support, and communications surrounding the HPAI virus cases impacting lactating dairy cattle.

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  • Figure 1 . Mammary gland lesions in cattle in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. A, B) Mammary...
  • Figure 2 . Lesions in cat tissues in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Tissue sections were stained...
  • Figure 3 . Phylogenetic analysis of hemagglutinin gene sequences in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Colors indicate...
  • Figure 4 . Phylogenetic analysis of neuraminidase gene sequences in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Colors indicate...
  • Table 1 . Microscopic lesions observed in cattle in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024
  • Table 2 . Microscopic lesions observed in cats in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024
  • Table 3 . PCR results from various specimens in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024

Suggested citation for this article : Burrough ER, Magstadt DR, Petersen B, Timmermans SJ, Gauger PC, Zhang J, et al. Highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Emerg Infect Dis. 2024 Jul [ date cited ]. https://doi.org/10.3201/eid3007.240508

DOI: 10.3201/eid3007.240508

Original Publication Date: April 29, 2024

Table of Contents – Volume 30, Number 7—July 2024

Please use the form below to submit correspondence to the authors or contact them at the following address:

Eric R. Burrough, Iowa State University Veterinary Diagnostic Laboratory, 1937 Christensen Dr, Ames, IA 50011, USA

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