H7N9 influenza: What you should know now

Dr. Michael Jhung,
medical officer for the influenza division,
Centers for Disease Control and Prevention

A new flu virus has recently emerged in China, putting health officials around the world, including those at the U.S. Centers for Disease Control and Prevention, on alert. Today’s guest blog post by Dr. Michael Jhung, medical officer for the influenza division, Centers for Disease Control and Prevention, provides a status report of flu activity as of April 18, 2013, and tells you what you need to know about this novel virus that to date has led to 87 confirmed illnesses and 17 deaths.

Not long after a newsworthy 2012-2013 influenza season, flu is in the headlines again. On April 1, the World Health Organization first reported three 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 the Centers for Disease Control and Prevention, we are following this situation closely, coordinating with domestic and international partners, taking routine preparedness steps and sharing frequent updates.

Here are some 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, please visit our H7N9 page.
2. There are no 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 CDC’s 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 humans infected with 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 its live poultry markets for the time being.
4. On Thursday, 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.
5. CDC also is using the virus isolate from China to:
• Develop a test kit for detecting H7N9 infections in humans.
• 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.
• 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 — or 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.

Visit cdc.gov for more information on human-to-human transmission. 


About the author:
Michael Jhung, MD, MPH, MS, is a medical officer for the Surveillance and Outbreak Response Team in the Influenza Division, National Center for Immunization and Respiratory Diseases, at the Centers for Disease Control and Prevention in Atlanta, Georgia. Dr. Jhung received his Bachelor of Science in Kinesiology from University of Michigan in 1989 and his Master of Science in Bioengineering from the University’s College of Engineering in 1994. He completed his doctorate of medicine from Case Western Reserve University School of Medicine in 2002, and his Master of Public Health in Epidemiology from University of Michigan’s School of Public Health in 2004.

Dr. Jhung began working with CDC’s Division for Healthcare Quality Promotion in 2005 as an Epidemic Intelligence Officer, where he conducted surveillance for healthcare-associated adverse events and rapidly responded to requests for assistance with investigation of health-care associated infections. Dr. Jhung graduated from the EIS program and joined Influenza Division’s Surveillance and Outbreak Response Team in 2009, where he has applied his expertise to responding to influenza outbreaks, providing scientific training of Fellows and staff, and contributing key findings to CDC’s pandemic preparedness plans.

Mutant flu research in the news

If you’ve paid attention to the news recently, you may have heard about researchers who created “mutant” bird flu in a lab. Sounds scary, right? Should you be worried about this human-made type of flu?

This so-called mutant flu was created from a combination of two strains of influenza, known as H5N1 and H1N1. The research was going on last year, but didn’t get major attention until December 2011, when the scientists tried to make their results public. Suddenly, the news was full of stories about a potentially dangerous form of flu. In the U.S., the National Science Advisory Board for Biosecurity stepped in and told the researchers that they were not allowed to share the details of their experiments. There were a lot of discussions, with health leaders such as the World Health Organization weighing in. In March, the science board decided to let the scientists publish their results. A team of researchers in Wisconsin published its study this week.

But why did these scientists want to make a mutant bird flu in the first place?

H5N1 is a type of influenza that has been very deadly to humans. It was discovered 15 years ago when a boy in Hong Kong died. Scientists found out that this new flu, H5N1, was carried by chickens. This flu is commonly called “avian” influenza in the news.

Although H5N1 is deadly to humans, it has mostly stayed in birds over the last decade and a half. And so far, H5N1 has not been able to spread from person to person. A few hundred people have died from H5N1 flu, but they are mostly people who come into close contact with chickens and other birds in countries like China, Indonesia, Egypt, India and Vietnam.

What scientists are afraid of is that H5N1 could someday mutate into a type of flu that could spread from person to person. Because humans have not been exposed to this kind of flu, we don’t have an immunity to H5N1, and our current flu vaccines wouldn’t protect us. Scientists fear that H5N1 could cause the next great flu pandemic.

So back to the mutant flu research. The scientists took wild H5N1, which can’t be spread person to person, and mixed it with parts of the H1N1 virus, which can spread to humans (and as we learned in 2009 during the global pandemic, it spreads quickly!) The researchers checked millions of viruses for mutations until they found a virus that could spread in mammals, and then they tested it. What they found was a little scary: It only took four small changes in the H5N1 virus to start spreading in the air. 

H5N1 viruses (colored gold) are grown in a lab.
Image courtesy CDC/Cynthia Goldsmith; Jacqueline Katz; Sherif R. Zaki

Were these scientists trying to create a dangerous new flu and start a big pandemic? Definitely not. The research was done to help us understand how flu viruses mutate so that we can better understand how to look for new types of flu — and hopefully stop them from spreading across the globe.

Thanks to these new studies, we now know how easily a person-to-person type of H5N1 flu may develop. But instead of being scared, we should be hopeful, because we’re also one step closer to a better flu vaccine and better ways to monitor the flu.

To learn more about H5N1 flu, visit WHO’s website. You can also learn more about the different types of flu through our post, “So, what causes the flu?”