Distributed via the CDC Health Alert Network
April 5, 2013, 10:00 a.m. ET
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.
These cases are a reminder that novel A influenza viruses can infect and cause severe respiratory illness in humans. Novel influenza A viruses are influenza viruses that are different from currently circulating human influenza A virus subtypes and include influenza viruses from predominantly avian and swine origin. In recent years, human infections with highly pathogenic avian influenza A (H5N1) virus in several Asian countries and Egypt, highly pathogenic avian influenza A (H7N3) virus in Mexico, and variant influenza A (H3N2)v viruses in the United States have been reported (www.cdc.gov/mmwr/preview/mmwrhtml/mm6136a4.htm, www.who.int/influenza/human_animal_interface/EN_GIP_20130312CumulativeNumberH5N1cases.pdf, emergency.cdc.gov/HAN/han00325.asp). The clinical presentation of human infection with avian influenza A viruses varies considerably--from mild illness, including conjunctivitis, fever, and cough, to severe illness, including fulminant pneumonia leading to death in cases of H5N1 and in these recent cases of H7N9 virus infections. To date there has been no evidence of person-to-person transmission of influenza A (H7N9) viruses.
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.
Clinicians should consider the possibility of novel influenza A (H7N9) virus infection in persons with respiratory illness and an appropriate travel or exposure history. Although the majority of novel influenza A (H7N9) cases have resulted in severe respiratory illness in adults, infection with this virus may cause mild illness in some and may cause illness in children as well. When performing influenza diagnostic testing in patients with respiratory illness for whom an etiology has not been confirmed, clinicians may identify human cases of avian influenza A virus infection or new cases of variant influenza in the United States. Patients with novel influenza A (H7N9) virus infections should have a positive test result for influenza A virus via reverse-transcription polymerase chain reaction (RT-PCR) testing but be unsubtypeable.
Suspected infections with novel influenza A (H7N9) viruses in the United States should be reported to CDC within 24 hours of initial detection, and state health departments should notify CDC promptly of all patients under investigation for possible novel influenza A virus infection.
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