Avian Influenza A (H7N9) Virus
By now you may have heard that a new strain of bird flu has been identified in China where a new virus – H7N9 – has infected chickens and pigeons sold in markets. On April 1, 2013, the World Health Organization (WHO) first reported 3 people had been sickened with the new virus. Since then, additional cases have been reported inside China.
The new H7N9 virus has not been detected in people or birds in the United States.
Most people with H7N9 have severe respiratory illness; some have died. The virus does not appear to be spreading from person-to-person at this time.
H7N9 – a New Bird Flu Virus
The new H7N9 virus is a bird flu – or “avian influenza” – virus. The new virus is very different from other H7N9 viruses previously found in birds. Birds infected with H7N9 do not show signs of being sick. Genetic information about the virus suggests that H7N9 may be able to infect people and other mammals more easily than previous avian influenza viruses.
This is the first time that bird flu H7N9 virus has been found in people.
Spread of H7N9
Human infections with bird flu are rare but have occurred in the past. Most probably these infections happen after contact with infected poultry. Many of the human cases of H7N9 are reported to have had contact with poultry. However, some cases reportedly have not had such exposure.
Critically important, no person-to-person spread of the H7N9 virus has been found. Based on previous experience with other bird flu viruses – most notably H5N1 – some limited person-to-person spread of this H7N9 virus would not be surprising. Close contacts of confirmed H7N9 patients are being watched for signs of human-to-human spread of H7N9.
Source of H7N9
At this point, it is too early to tell much about what course this virus will take. Although H7N9 has been found in birds, birds are not necessarily the source – sometimes called “reservoir” – of the infection. Until veterinary experts can learn more about the source of the virus and how it spreads, they can only speculate – which means to make guesses – based on what similar viruses have done in the past.
Still Much to Learn
This is a developing situation as the H7N9 virus continues to change – or to “mutate”. There is still much to learn. CDC is following this situation and working closely with national and partners around the world. With time, research will provide the answers we need.
For the Latest Information About Avian Influenza A H7N9 Bird Flu
To find answers to your questions about H7N9, please visit:
- Access the weekly report on number of confirmed human cases for avian influenza A(H7N9) reported to WHO
- Avian Influenza A (H7N9) Virus (CDC)
- Emergence of Avian Influenza A(H7N9) Virus Causing Severe Human Illness — China, February–April 2013 (CDC)
- H7N9: Frequently Asked Questions (CDC)
- Frequently Asked Questions on Human Infection with Influenza A(H7N9) Virus, China (WHO)
- Latest Disease Outbreak News (WHO)
Practice Usual Precautions: Avian Flu (H7N9) in China (CDC)
Source: Avian Influenza A (H7N9) Virus. Centers for Disease Control and Prevention (CDC).
For more information:
Go to the Pandemic Flu health topic.