Analysis on the molecular characteristics of the first human case of influenza A (H7N9) virus infection in Gansu province

Objective To analyze the discovery process and molecular characteristics of the first human case of influenza A (H7N9) virus infection in Gansu province, so as to provide scientific basis for the prevention and control of avian influenza in Gansu province. Methods For the case detection process, the respiratory tract samples from the patient were analyzed by real-time fluroscent PCR and the isolated strain was sequenced to analyze the genetic characteristics of hemagglutinin (HA) and neuraminidase (NA). Results The case had confirmed history of exposure to the environment contaminated by influenza A (H7N9) virus. The nucleic acids test results of the samples were positive for influenza A (H7N9) virus. The HA and NA genes of the isolated strain belong to the Yangtze River Delta strain of the Eurasian lineage and had high similarity with avian influenza A (H7N9) viruses isolated from poultry in Shandong province and Jiangsu province. Three mutations, G186V, T160A and Q226L occurred in HA protein. An additional glycosylation site NKS was observed at sites 165-167. sequence glycosylation at sites 22-24, 38-40, 240-242, 411-413 and 483-445 showed no significant change. Conclusions The first human case of avian influenza A (H7N9) virus infection in Gansu province showed high homology with the reported avian influenza A (H7N9) virus strains. Strengthening monitoring for mutations of the virus at the genetic level may help scientific prevention and control of the epidemics. Key words: Human case of influenza A (H7N9) virus infection; Etiology; Sequence analysis