Serological surveillance for avian influenza virus in environment and population with occupational exposure in Gansu, 2019–2020

  Objective  To understand the infection status of avian influenza virus in population with occupational exposure s in Gansu province from 2019 to 2020 and the contamination of avian influenza viruses in the environment of live poultry markets, and provide evidence for the prevention and control of human infection with avian influenza virus.

  Methods  Environmental samples such as surface swabs of poultry cages and feces of poultry, were collected from live poultry markets in Gansu. Real-time fluorescent RT-PCR was used to detect nucleic acid of influenza A virus in the samples. The positive samples were then tested for nucleic acid of H5, H7 and H9 subtypes of avian influenza virus. At the same time, serum samples from population with occupational exposure to avian influenza virus were collected, and the hemagglutination inhibition (HI) method was used to detect the antibodies to avian influenza A (H5N6),A (H7N9), and A (H9N2) viruses.

  Results  A total of 5 225 environmental samples were collected from 2019 to 2020, in which 1 069 were positive (20.46%); the predominant strains belong to subtype H9, and there were 14 mixed infections of subtype H7 and H9 viruses; the positive rate in Dingxi was highest (40.79%), followed by Tianshui (40.00%), Longnan (37.63%), Baiyin (31.05%) and Jiayuguan (26.35%). The positive rate of avian influenza virus was highest (46.16%) in poultry chopping board swabs (46.26%) and lowest in poultry drinking water samples (15.71%). The difference was significant (χ²=21.038, P<0.05). Seven serum H9 antibody positive samples were detected in 437 persons with occupational exposures.

  Conclusion  Avian influenza virus contamination in the environment of live poultry markets in Gansu was mainly caused by subtype H9 virus, subtype H7 was sporadically detected, and no subtype H5 virus was detected, and there was less latent H9N2 virus infection in the population with occupational exposures. Active surveillance should be strengthened to prevent the outbreak of human infection with avian influenza virus.