Quantification of Airborne Influenza and Avian Influenza Virus in a Wet Poultry Market using a Filter/Real-time qPCR Method

Influenza viruses cause pandemics in humans. The aim of this study was therefore to evaluate filter/real-time qPCR to quickly and accurately determine and quantify the airborne influenza and avian influenza virus. In this study, the sampling stress of filtration to influenza virus and the storage effects for both the virus and extracted RNA were evaluated in the laboratory. Then, the collection efficiencies of open-face and closed-face filter cassettes were compared in a wet poultry market. From July 8 to August 19, 2006, a total of 36 air samples were quantified by filter/real-time qPCR. The recovery rate of the virus on a filter stored at 4C reached 0.94 after 3-day storage, whereas the RNA stored at -80C was 100% after 3-month storage. In terms of collection efficiency, the closed-face filter cassette was superior to the open-face filter cassette in the field study. In the wet poultry market, it was revealed that both the positive rate and concentration of influenza A virus in the chicken pen were higher than that in the duck pen, possibly due to differences in ventilation type, climate factors, and avian characteristics. To our knowledge, this is the first report describing the quantification of airborne influenza virus in field samples. This quantitative technique should provide more insight into influenza/avian influenza virus transmissibility and epidemiology of influenza/avian influenza, as well as infection control.