Avian Influenza A (H7N9) Virus
The World Health Organization (WHO) has reported a number of human infections with avian influenza A (H7N9) viruses in China. The first cases were announced by WHO on April 1, 2013. Updates are available on the WHO website.
This is the first time avian influenza A (H7N9) viruses have been detected in humans. The infections so far have resulted in severe respiratory illness and, in some cases, death. According to WHO, no human-to-human transmission has been identified at this time, and the cases do not have a known epidemiological link to one another. An investigation by Chinese health authorities is ongoing to determine the source of infection and detect any additional cases. The sequences of these viruses are posted and publicly available in GISAID.
CDC is following this situation closely and coordinating with domestic and international partners in a number of areas, including gathering more information to make a knowledgeable public health risk assessment and developing a candidate vaccine virus. CDC also is reviewing posted genetic sequencing of the new H7N9 viruses and assessing possible implications in terms of the viruses’ transmissibility and severity and whether existing influenza diagnostic tests need to be enhanced or new ones developed. All of these actions are routine preparedness measures taken whenever a new novel influenza virus is detected in humans.
This is an evolving situation and there is still much to learn. CDC will provide updated information as it becomes available.
General information about avian influenza viruses and how they spread is available at Avian Influenza A Virus Infections in Humans.
WHO has posted Frequently Asked Questions on human infection with A(H7N9) avian influenza virus, China.
The Chinese Center for Disease Control and Prevention has posted a Question & Answer document related to this situation available at “Questions and Answers about human infection withA(H7N9) avian influenza virus.”
The European Centre for Disease Prevention and Control has published a rapid assessment on the emergence of the H7N9 virus in China available at “Rapid risk assessment: Severe respiratory disease associated with a novel influenza A virus, A(H7N9) China.”
Note: International cases of novel influenza A are reportable to the World Health Organization under the International Health Regulations. CDC will report only the H7N9 cases officially reported by WHO. There may be reporting delays as a result of this process.
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