H7N9 is a subtype of influenza A viruses that is sometimes found in birds, but that does not usually affect humans. Many H7 viruses have circulated in poultry for centuries. However, beginning at the end of March 2013, China reported the first new cases of infections spread from birds to people with a new strain of H7N9, which was very different from previously known H7N9 viruses. Although the transmission of the virus to humans has remained sporadic, it has steadily increased to where in May 2017, China reported 688 human infections to the World Health Organization (WHO). This increasing number of human infections has raised serious concerns by WHO and also the federal Centers for Disease Control and Prevention (CDC).
Poultry infected with H7N9 virus do not experience any symptoms or signs of illness, yet they can transmit the virus to humans. To date, most of the reported human cases have experienced severe illness, beginning with high fever and cough, and frequently progressing to pneumonia. About 40% of these reported human cases have died. Although the H7N9 virus continues to have the greatest potential to cause a worldwide pandemic, presently there is no evidence of “sustained” spread of the virus from person to person. Ongoing spread of a virus among humans is necessary for a pandemic (global outbreak) to occur. Health officials are watching the situation closely for this.
Currently there is no publicly available vaccine to protect against H7N9 infection. Most of the H7N9 viruses which have been studied, however, appear to be susceptible to the three influenza antiviral drugs (oral oseltamivir, inhaled zanamivir and intravenous peramivir) that are recommended in the treatment of seasonal influenza.
No H7N9 virus infections of birds or humans have been detected in the United States so far, and at this time, the risk to people in the U.S. is considered to be very low. What about travel to China? Because H7N9 is not spreading easily from person to person, CDC and WHO are not recommending that people delay or cancel trips to China. CDC does advise travelers to China to take some common sense precautions such as not touching birds or other animals, avoiding live poultry markets, and washing hands often. All poultry and poultry products should be fully cooked.
It is always of significant public health concern whenever a new influenza A virus subtype (e.g. H7N9) that infects humans and causes severe illness emerges. For this reason, CDC, together with domestic and international partners such as WHO, continues to closely monitor the situation in China, with the goal of averting the possibility of a worldwide pandemic of H7N9 influenza.
For additional information visit: https://www.cdc.gov/flu/avianflu