[Epidemiological investigation on the first case of human avian influenza A (H7N9) virus infection in Beijing, 2013].

Objective To investigate and to analyze the first human case of avian influenza A (H9N2) virus infection in Beijing. Methods The relatives of the case were interviewed to investigate the process of morbidity and possible infection sources. Samples of the case, close contacts as well as environmental samples were collected and were tested by real-time PCR for nucleic acids of influenza A (H9N2) virus. Hemagglutinin (HA) genes of the viruses from the case and environment samples were sequenced and analyzed. Results The main clinical manifestations of the case were wild influenza-like symptoms and signs, with a history of exposure to live poultry market 15 days prior to the onset of illness. The positive rate of avian influenza A (H9N2) virus collected from that market was 18.2%. Based on the phylogenetic analyses, the amino acid homology between the viruses isolated from the case and environment reached 100%, and both of them belonged to the Eurasian lineage. Neither fever nor respiratory symptoms were found in all 4 close contacts during the medical observation period. Conclusions This case of avian influenza A (H9N2) virus infection was associated with exposure to live poultry market. Enhanced surveillance for influenza and supervision for live poultry market is important to the prevention and control of avian influenza infections. Key words: Avian influenza; H9N2; Epidemiology