An investigation into the potential role of aerosol dispersion of dust from poultry barns as a mode of disease transmission during an outbreak of avian influenza (H7:N3) in Abbotsford, BC in 2004.

摘要

During the winter and spring of 2004, an avian influenza outbreak occurred in the Lower Fraser Valley of British Columbia. In the early stages of the outbreak, the infected premises were fairly close together (within 2 to 3 km of one another) and downwind from the prevailing NE winds on the Matsqui Prairie at that time of year. While the scientific literature does not define wind movement as a principle source of avian influenza virus transfer, discussions with scientific leaders in the field of avian influenza from Italy, the Netherlands, and the United Kingdom in April 2004 revealed markedly divergent opinions from "highly sceptical" to "a considerable factor to deal with". Clearly revealed was the absence of any testing to support or refute a windborne theory of transmission during recent outbreaks in Italy and the Netherlands. A preliminary assessment of the likelihood of wind playing a role in transmission involved the use of hourly weather data provided by Environment Canada and BC Water Land and Air Protection. This assessment was followed by a more analytic approach provided by the mathematical plume models of the Meteorological Service of Canada's Emergency Response Division. A field study was conducted in early April to evaluate if avian influenza virus was being spread into surrounding areas on dust particles emitted from barns containing infected birds. Air sampling conducted inside an infected barn revealed a high quantitative estimate of viral load per cubic meter of air of 292 TCID50. Outdoor samples using low volume air samplers were all negative for the presence of virus. High volume air sampling conducted outdoors confirmed that avian influenza virus was circulating in the air outside barns during the outbreak, yet it remained unclear if the virus was alive and therefore potentially infectious. Current and future plans to further understanding of aerosol dispersion involve collaborations with academia and other government departments. A planned field study will aim to validate models for predicting the movement of generic biological agents from livestock barns into the surrounding environment..