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Avian Influenza A (H7N9) Virus
Human infections with a new avian influenza A (H7N9) virus continue to be reported in China. The virus has been detected in poultry in China as well. While mild illness in human cases has been seen, most patients have had severe respiratory illness and some people have died. The only case identified outside of China was recently reported in Malaysia. The new H7N9 virus has not been detected in people or birds in the United States.
An investigation by Chinese authorities is ongoing. Many of the people infected with H7N9 are reported to have had contact with poultry. However some cases reportedly have not had such contact. Close contacts of confirmed H7N9 patients are being followed to determine whether any human-to-human spread of H7N9 is occurring. No sustained person-to-person spread of the H7N9 virus has been found at this time.
Human infections with avian influenza (AI, or “bird flu”) are rare but do occur, most commonly after exposure to infected poultry (Bird-to-human spread). Limited person-to-person spread of bird flu is thought to have occurred rarely in the past, most notably with avian influenza A (H5N1). Based on this previous experience, some limited human-to-human spread of this H7N9 virus would not be surprising. Most important, however, is that this transmission not be sustained (ongoing).
Influenza viruses constantly change and it’s possible that this virus could become able to easily and sustainably spread between people, triggering a pandemic. CDC is following this situation closely and coordinating with domestic and international partners. CDC takes routine preparedness actions whenever a new virus with pandemic potential is identified, including developing a candidate vaccine virus to make a vaccine if it were to be needed. CDC also has issued guidance to clinicians and public health authorities in the United States, as well as provided information for people traveling to China. This is an evolving situation and there is still much to learn. CDC will provide updated information as it becomes available.
H7N9 Frequently Asked Questions…
Links to Publications, Resources, and WHO FAQ related to H7N9…
Guidance and info for public health professionals, clinicians and laboratorians
In The News
Electron Micrograph Images of H7N9 Virus from China…
Historic H7N9 Information
Archive of H7N9 Information and Resources
H7N9: What should I do?
- CDC does not have any new or special recommendations for the U.S. public at this time regarding H7N9. CDC will keep you updated. Stay informed.
- Since H7N9 is not spreading easily from person to person at this time, CDC does not recommend that people delay or cancel trips to China. The World Health Organization also is watching this situation closely and does not recommend any travel restrictions.
- CDC advises travelers to China to take some common sense precautions, like not touching birds or other animals and washing hands often. Poultry and poultry products should be fully cooked. CDC will update its advice for travelers if the situation in China changes. This guidance is available at Avian Flu (H7N9) in China.
Genetic Evolution of H7N9 Virus in China, 2013
The eight genes of the H7N9 virus are closely related to avian influenza viruses found in domestic ducks, wild birds and domestic poultry in Asia. The virus likely emerged from “reassortment,” a process in which two or more influenza viruses co-infect a single host and exchange genes. This can result in the creation of a new influenza virus. View Infographic