Outbreaks
of avian influenza virus (AIV) have raised public concerns
recently. Airborne AIV has been evaluated in live poultry markets
and case farms; however, no study has discussed airborne AIV in ambient
air in the winter habitats of migratory birds. Therefore, this study
aimed to evaluate airborne AIV, specifically H5, H7, and H9, in a
critical winter habitat of migratory birds and assess the factors
influencing airborne AIV transmission in ambient air to provide novel
insights into the epidemiology of avian influenza. A total of 357
ambient air samples were collected in the Aogu Wetland, Taiwan, Republic
of China, between October 2017 and December 2019 and analyzed using
quantitative real-time polymerase chain reaction. The effects of environmental
factors including air pollutants, meteorological factors, and the
species of the observed migratory birds on the concentration of airborne
AIV were also analyzed. To our knowledge, this is the first study
to investigate the relationship between airborne AIV in ambient air
and the influence factors in the winter habitats of migratory birds,
demonstrating the benefits of environmental sampling for infectious
disease epidemiology. The positive rate of airborne H7 (12%) was higher
than that of H5 (8%) and H9 (10%). The daily mean temperature and
daily maximum temperature had a significant negative correlation with
influenza A, H7, and H9. Cold air masses and bird migration were significantly
associated with airborne H9 and H7, respectively. In addition, we
observed a significant correlation between AIV and the number of pintails,
common teals, Indian spot-billed ducks, northern shovelers, Eurasian
wigeons, tufted ducks, pied avocets, black-faced spoonbills, and great
cormorants. In conclusion, we demonstrated the potential for alternative
surveillance approaches (monitoring bird species) as an indicator
for influenza-related risks and identified cold air masses and the
presence of specific bird species as potential drivers of the presence
and/or the airborne concentration of AIV.
