Human Infections with Novel Influenza A (H7N9) Viruses

Summary and Background

As of April 4, 2013, Chinese public health officials have reported 14 cases of human infection with a novel avian influenza A (H7N9) virus from four different provinces in China. All patients were hospitalized with severe respiratory illness, and six persons have died. These are the first human infections identified with an avian influenza A (H7N9) virus infection. Six cases are from Shanghai, one is from Anhui Province, four are from Jiangsu Province, and three are from Zhejiang Province. Thirteen cases are in adults aged 27 through 87 years, and one case is in a child aged 4 years; all cases had illness onset from February 19 through March 31, 2013. No person-to-person transmission or epidemiologic link between any of the cases has been identified. We are aware of reports of possible sources of infection but these have not been confirmed. We are investigating and will provide that information when it is available.

Preliminary functional data of the isolated viruses from the first 3 cases suggest that they are likely susceptible to neuraminidase inhibitors. Investigations by Chinese public health officials are ongoing.

At this time, no cases of human infection with avian influenza A (H7N9) viruses have been detected in the United States. Rapid detection and characterization of novel influenza viruses remain a critical component of national efforts to prevent further cases, evaluate clinical illness associated with them, and assess any ability for these viruses to spread among humans. As a result, clinicians are reminded to consider influenza as a possible diagnosis when evaluating patients with acute respiratory illnesses, including pneumonia, even outside of the typical influenza season.