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H7N9 Influenza: 6 Things You Should Know Now

Categories: Disease Detectives, Emergency Preparedness & Response, Global Health Threats, Public Health Partners

Image of the H7N9 virus courtesy of Cynthia S. Goldsmith and Thomas Rowe

Not long after a newsworthy 2012-2013 influenza season, flu is in the headlines again. On April 1, the World Health Organization (WHO) first reported 3 human infections with a new influenza A (H7N9) virus in China. Since then, additional cases have been reported. Most of the people reportedly infected have had severe respiratory illness and, in some cases, have died.

Fortunately, there are currently no reported cases of H7N9 in the U.S. or anywhere outside of China.  At CDC, we are following this situation closely, coordinating with domestic and international partners, taking routine preparedness steps, and sharing frequent updates.

Here are six things you should know about the current H7N9 situation:

  1. It is still early in the response and there is a tremendous amount that we don’t know. Our information is likely to be updated and change frequently as we learn more about H7N9. To stay informed, visit CDC’s H7N9 Virus webpage.
  2. There are not any confirmed cases of human infection in the U.S. and there is currently no evidence that the virus can spread in a sustained way from person-to-person. Other than advice for travelers or people who are ill, CDC is not making any additional or special recommendations for U.S. public action specific to H7N9. Travelers should continue to visit CDC’s Travelers’ Health page on H7N9 for current travel recommendations.
  3. After the first human infections with H7N9 were detected in China, Chinese authorities detected H7N9 viruses in poultry in the same area where human infections have occurred. China is investigating cases, their exposures and their contacts closely. Many of the human cases of H7N9 are reported to have had contact with poultry. The current working assumption is that most human infections with H7N9 have resulted from exposure to infected birds or contaminated environments. The extent of the outbreak in poultry is still being assessed, but China has reportedly begun removing birds from live markets. Shanghai is currently taking extra precautions by closing down their live poultry markets for the time being.
  4. On April 11, CDC received the first H7N9 virus isolate from China. Since this H7N9 virus is new and has pandemic potential, we are using the virus isolate from China to develop a candidate vaccine virus that could be used to make a vaccine if one is needed.

    Dr. Michael Jhung, CDC

  5. CDC also is using the virus isolate from China to:
    1. Develop a test kit for detecting H7N9 infections in humans.
    2. Test for the presence of antibodies against the H7N9 virus in human blood samples. This will allow CDC to see if some people already have immunity against this virus.
    3. Test to see whether existing antiviral drugs (i.e. Tamiflu and Relenza) will work to treat people who become ill from H7N9.
  6. The investigation in China has not revealed any sustained (ongoing) human-to-human spread of this virus, but non-sustained human-to-human spread of bird flu viruses has occurred in the past (most notably with H5N1). It’s likely that some limited human-to-human spread of H7N9 will occur. Sustained, community transmission is needed for a pandemic to start.

For more information on human-to-human transmission, visit:

Public Comments

Comments listed below are posted by individuals not associated with CDC, unless otherwise stated. These comments do not represent the official views of CDC, and CDC does not guarantee that any information posted by individuals on this blog is correct, and disclaims any liability for any loss or damage resulting from reliance on any such information. Read more about our comment policy ».

  1. April 27, 2013 at 4:41 am ET  -   Protego

    Excellent concise summary – it is a pity about the confusion between the ‘old’ H7N9 avian influenza which was a mild disease of poultry and never infected humans with this triple reassortant new virus – it is now never clear which virus and which test is being refered to when it is research in birds! (and which is pictured vH7N9 or H7N9?)
    The similarities between the epidemiology of vH7N9 and Saudi SARS – sporadically infecting elderly males with a course of three weeks is not actually alarming – the obvious possibility to rule in/out is whether smokers are inhaling it deep into their lungs where the receptor cells are because both Arab and Chinese men are some of the heaviest smokers in the world – their womenfolk are not!
    The real worry is that this H7 virus – which proved impossible to make a mock-up vaccine for in 2008 – will reassort in a pig or child with say H1N1 and become contagious between people. When/if that happens the starting gun is fired and those not prepared are in a scary position. In Vietnam this month three young people have died of H1N1 Swine Flu rapidly and with their lungs ‘destroyed’ – reminiscent of the cytokine storm seen in the 1918 pandemic.
    This is why we need constant vigilance but also to take the CDC ‘Do On Thing’ very seriously because whichever virus it turns out to be (perhaps a mutated Saudi SARS?) those who are prepared will emerge stronger in the post-pandemic ‘new’ world.

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  2. AUTHOR COMMENT May 7, 2013 at 12:44 pm ET  -   CDC - Blogs - CDC Works For You 24/7 Blog – CDC Scientists Produce Speedy Results Analyzing H7N9 Virus

    […] People continue to be infected with H7N9 bird flu in China. Fortunately, there is no evidence that this virus is spreading from person-to-person the way seasonal flu does. However, flu viruses are constantly changing and this virus could gain the ability to spread easily among people. At CDC, we are working around-the-clock in China and at home to respond to the global threat posed by H7N9.  We are monitoring the situation closely, coordinating response efforts with international and domestic partners, and keeping the public and health providers informed (check out the H7N9 webpage and our recent blog post, H7N9 Influenza: 6 Things You Should Know Now). […]

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  3. June 27, 2013 at 8:47 pm ET  -   test

    great post.

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