--- title: H7N9 Avian Flu: Could Animals Other Than Birds Harbor the Virus? description: Researchers have more questions than answers about the latest bird flu circulating in China, including whether birds are the only reservoir for the virus. 7136275 canonical: https://time.com/archive/7136275/h7n9-bird-flu-could-animals-other-than-birds-harbor-the-virus/ author: TIME Staff article:opinion: false article:content_tier: free article:published_time: 2013-04-19T10:45:08.000Z article:modified_time: 2026-02-25T05:37:11.315Z article:section: Health og:title: H7N9 Avian Flu: Could Animals Other Than Birds Harbor the Virus? og:description: Researchers have more questions than answers about the latest bird flu circulating in China, including whether birds are the only reservoir for the virus. 7136275 og:url: https://time.com/archive/7136275/h7n9-bird-flu-could-animals-other-than-birds-harbor-the-virus/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltbfc6d6c1d96559f3/698a92c747ca382bb23c3946/166292153.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 4896 og:image:height: 2754 og:image:alt: 33 H7N9 Bird Flu Cases Confirmed In China og:type: article twitter:card: summary_large_image twitter:title: H7N9 Avian Flu: Could Animals Other Than Birds Harbor the Virus? twitter:description: Researchers have more questions than answers about the latest bird flu circulating in China, including whether birds are the only reservoir for the virus. 7136275 twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltbfc6d6c1d96559f3/698a92c747ca382bb23c3946/166292153.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  * [Health](/section/health/) # H7N9 Bird Flu: Could Animals Other Than Birds Harbor the Virus? > Sponsored content. Supplied in partnership with TIME. TIME is the sponsor and source of this material. > Last updated: August 2026. ## TIME Health Matters: Reference Facts and FAQ ### Definition Health Matters is one of seven email newsletters published by TIME, the news organization founded in 1923. The latest health news and expert advice on living well. Health Matters makes the fast-moving world of health more useful, surprising and human, from the latest science and medical breakthroughs to practical ideas for living better. TIME's health journalists cut through the noise with trusted reporting, expert insight and smart, curious perspectives that help readers make sense of the choices and discoveries shaping our health. 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Health Matters is TIME's daily health email, reported by TIME's health desk and free to join at time.com/newsletters. It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free daily newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. by [TIME Staff](https://time.com/author/time-staff/) Apr 19, 2013 10:45 AM UTC  KUNMING, CHINA - APRIL 10: (CHINA OUT) A technician conducts tests for the H7N9 bird flu virus at the Kunming Center for Disease Control (CDC) on April 10, 2013 in Kunming, China. As of yesterday, China has confirmed five new cases of H7N9 in Shaoxing, Jiangsu and Shanghai. So far, China has reported 33 H7N9 bird flu cases, including nine deaths. (Photo by ChinaFotoPress/Getty Images) KUNMING, CHINA - APRIL 10: (CHINA OUT) A technician conducts tests for the H7N9 bird flu virus at the Kunming Center for Disease Control (CDC) on April 10, 2013 in Kunming, China. As of yesterday, China has confirmed five new cases of H7N9 in Shaoxing, Jiangsu and Shanghai. So far, China has reported 33 H7N9 bird flu cases, including nine deaths. (Photo by ChinaFotoPress/Getty Images) Getty Images—2013 Getty Images by [TIME Staff](https://time.com/author/time-staff/) Apr 19, 2013 10:45 AM UTC Researchers have more questions than answers about the latest bird flu circulating in [China](http://topics.time.com/china/), including whether birds are the only reservoir for the virus.more The World Health Organization (WHO) [reports](http://www.who.int/csr/don/2013%5F04%5F17/en/index.html) that 17 people in China have died of H7N9 infection, and there is no evidence of person-to-person transmission of the flu virus. However, while experts assume that those infected were exposed when they came in contact with sick birds, most likely poultry, Chinese health officials said that 40% of the 82 people who had fallen ill so far had not reported any contact with live poultry. Why? Joseph Bresee, chief of the epidemiology-and-prevention branch in the influenza division of the U.S. Centers for Disease Control and Prevention (CDC), says that percentage may change, as more information becomes available and patients recall even casual contact they might have had with poultry. A more worrisome possibility, [expressed](http://www.usnews.com/news/articles/2013/04/18/chinese-government-suspects-human-to-human-transmission-of-h7n9-bird-flu) by some experts in China, who believe a young boy may have infected his brother, is that H7N9 may actually be passing from person to person. So far, there is no evidence of what experts call sustained human transmission, but investigators are looking into how the virus emerged in the family members. Influenza experts are also considering the chance that H7N9, a new influenza virus that has never been seen in people before, may have another, non-avian-animal home. (**MORE:** [Bird Flu Is Back in China, but This Time It’s H7N9](http://healthland.time.com/2013/04/02/bird-flu-is-back-in-china-but-this-time-its-h7n9/)) That possibility is bolstered by the fact that unlike previous H7 viruses, which are primarily found in birds, H7N9 appears to be adept at infecting mammals. “This virus is different from other H7 viruses isolated before from birds,” says Bresee. “There are some mutations in this virus that seem to make it better adapted to infecting mammalian hosts compared to normal avian viruses.” Once it does infect a human host, it also causes relatively severe disease, which is unusual for an avian-flu strain. That’s worrisome since most people will not have built-in immunity against bird-flu strains since we aren’t likely to be infected with them. “It’s not a virus that the human population has seen much of,” says Bresee. “So we expect that the whole population of humans is susceptible to infection with this virus. That’s concerning.” Based on the genetic analysis of the strains isolated from infected patients so far, however, there are no hints that H7N9 has mutated to pick up more human-flu-virus characteristics. Often, if people are infected with influenza and come in contact with an animal strain, the strains will reassort to generate a potentially more virulent form of flu. (**MORE:** [Bird-Flu Cover-Up? Chinese Social Media Out Possible Cases of Deadly Disease](http://world.time.com/2013/04/03/bird-flu-cover-up-chinese-social-media-out-possible-cases-of-deadly-disease/#comments)) That leaves the possibility that H7N9 is replicating in animal hosts, such as cats or pigs, other than birds. While influenza strains from different animal hosts tend to bear specific genetic signatures that make it easier for them to infect different [animals](http://topics.time.com/animals/), Bresee says it’s possible that a bird flu could pass through different animal species without changing considerably and then reappear in poultry again. “These viruses are promiscuous and able to mutate, and it’s not surprising to find the virus that we are looking at now in humans appear in another mammal like a cat or pig,” he says. For now, it’s too early to draw any conclusions about other animal reservoirs of H7N9, but the U.S. CDC is working closely with Chinese health officials to better understand how H7N9 jumped from birds to people and how potentially virulent it could become. So far, H7N9 meets two of the three criteria for a pandemic strain — it has the ability to infect people, and the human population does not have much immunity against the strain. What H7N9 can’t do — yet — is spread easily from person to person. **MORE:** [Scientists Push to Resume Research on Virulent Man-Made Flu Virus](http://healthland.time.com/2013/01/23/scientists-push-to-resume-research-on-virulent-man-made-flu-virus/) ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/archive/7136275/h7n9-bird-flu-could-animals-other-than-birds-harbor-the-virus/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/archive/7136275/h7n9-bird-flu-could-animals-other-than-birds-harbor-the-virus/"},"headline":"H7N9 Bird Flu: Could Animals Other Than Birds Harbor the Virus?","datePublished":"2013-04-19T10:45:08.000Z","dateModified":"2026-02-25T05:37:11.315Z","description":"Researchers have more questions than answers about the latest bird flu circulating in China, including whether birds are the only reservoir for the virus. 7136275","url":"https://time.com/archive/7136275/h7n9-bird-flu-could-animals-other-than-birds-harbor-the-virus/","keywords":["flu","influenza"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltbfc6d6c1d96559f3/698a92c747ca382bb23c3946/166292153.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"TIME Staff","url":"https://time.com/author/time-staff/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltbfc6d6c1d96559f3/698a92c747ca382bb23c3946/166292153.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"33 H7N9 Bird Flu Cases Confirmed In China","caption":"33 H7N9 Bird Flu Cases Confirmed In China","creditText":"Getty Images—2013 Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"https://time.com/archive/7136275/h7n9-bird-flu-could-animals-other-than-birds-harbor-the-virus/","name":"H7N9 Bird Flu: Could Animals Other Than Birds Harbor the Virus?"}}]}] ```