A small-scale study on airborne transmission of H9N2 avian influenza virus under field conditions

Abstract

Introduction: H9N2 avian influenza viruses (AIV) can transmit in chicken flocks through direct contact and aerosols. Nevertheless, data on airborne transmission of AIV is very limited, especially under field conditions. To fill this literature gap, this study was designed to investigate airborne transmission of H9N2 AIV originating from infected chicken flocks under field conditions, with the aim to further characterize the airborne transmission of H9N2 AIV. Methodology: Oropharyngeal swabs were collected from different diseased chickens to confirm H9N2 AIV infection. All glass impingers 30 (AGI-30) were used to collect indoor, upwind and downwind air samples for three chicken houses with H9N2 AIV infected chickens. Swabs and air samples were tested for H9N2 AIV using a real-time reverse transcription polymerase chain reaction (RRT-PCR). H9N2 AIV was isolated in embryonated chicken eggs and hemagglutinin (HA) gene sequence similarity of the isolated AIV was compared. Results: The results showed that indoor air samples were all RRT-PCR positive for H9N2 AIV. Downwind air samples collected between 10 m and 1.5 km away from the chicken houses were also found positive with an average load 2.62-5.21×10

A H9N2 Human Case and Surveillance of Avian Influenza Viruses in Live Poultry Markets — Huizhou City, Guangdong Province, China, 2021

“…So far in 2021, 11 human infections with A/H9N2 have been reported (2-3). Among them, Guangdong Province reported four cases, Yunfu City reported two cases, Meizhou City and Huizhou City each reported one case (4)(5). According to the routine influenza surveillance of Huizhou City, avian influenza A virus had a high positivity rate in poultry markets with subtype H9 being the most common subtype of avian influenza virus in poultry.…”

“…Combined with the epidemiological investigation, clinical symptoms of the patient, and the surveillance of avian influenza in the live poultry market, it is believed that the cause of the disease was mainly associated with exposure to the market that was contaminated by H9N2 avian influenza viruses. Therefore, she was likely infected by inhaling aerosols containing viruses ( 6 ).…”

Airborne Avian Influenza Virus in Ambient Air in the Winter Habitats of Migratory Birds

“…Aerosol transmission has been verified to be a critical route for AIV transmission in both chamber − and field studies. ,− The positive rates and concentrations of airborne influenza virus RNA in live poultry markets (LPMs) and on poultry farms are listed in Table S2. In LPMs, the positive rate was in the range of 11 to 90%, ,− with 3, 5, and 24% for airborne H5, H7, and H9, respectively, and only two studies have discussed the concentration with a range of 310 to 67,200 copies/m 3 .…”

“…In LPMs, the positive rate was in the range of 11 to 90%, ,− with 3, 5, and 24% for airborne H5, H7, and H9, respectively, and only two studies have discussed the concentration with a range of 310 to 67,200 copies/m 3 . For poultry farms, the positive rate of both H5N2 and H9N2 was 33%, and the concentration ranged from 5300 to 120,000 copies/m 3 (geometric mean) for H5N2 and 2620 to 67,200 copies/m 3 for H9N2. − In addition, airborne influenza virus was detected both inside the case farms (12,000 copies/m 3 for H5N2) and downwind (5300 copies/m 3 for H5N2 at 150 m) from the case farms, − indicating that airborne transmission of AIV may be mediated by wind.…”

“…Factors influencing airborne AIV transmission, including wind-mediated transportation, the number of infected birds (sources), climatic factors, and air pollutants have been analyzed. − ,− Airborne AIV has been detected in the downwind area of Asian dust storms (ADSs) and in poultry farms, having traveled through wind-mediated transportation, − indicating that airborne AIV in ambient air may be affected by wind-mediated transportation, including dust storms and cold air masses. Migratory birds may also introduce AIV into different countries, causing AIV outbreaks. − The numbers and species of migratory birds may play a critical role in the spread of AIV.…”