Infection source of the first case of human infection with avian influenza A (H7N9) virus in Daxing district of Beijing, 2017

Objective To understand the infection source of the first case of human infection with avian influenza A (H7N9) virus in Daxing district of Beijing in 2017, and provide scientific evidence for the prevention and control of human H7N9 virus infection.

Methods Field epidemiological investigation and laboratory testing method were used to trace the possible source of infection.

Results The exposure to live poultry of the case occurred one week before the onset of the disease. Throat swabs, deep cough sputum fluid, and serum samples of case were nucleic acid positive for H7N9 virus. H7N9 virus nucleic acid was detected in both live poultry and its environment. Seven other exposed individuals and close contacts were found to be nucleic acid negative. Sequencing analysis of hemagglutinin (HA) gene and neuraminidase (NA) gene showed no significant variation.

Conclusion Live poultry exposure history was one of key risk factors of H7N9 virus infection. The source of infection was live poultry purchased from a floating market. The sequencing of the virus and the HA0 cleavage site of the virus indicated that the virus belongs to the virus of H7N9 Yangtze River Delta branch and is a low-pathogenic avian influenza virus.