School of Public Health

Daniel Smith

Determining the effects of meteorological conditions on West Nile virus seasons in Washington State

West Nile virus (WNV) is a global threat to public health. Culex pipiens and Culex tarsalis, the WNV vectors found in Washington state (WA), activity has been linked to environmental variables in previous research across the world but little has been done in WA. Understanding how environmental factors affect WNV vectors may help guide public health efforts to stem its spread. We examined mosquito and climate data over 10 years (2008-2017) to examine how temperature and precipitation, during multiple periods within each year, affect C. pipiens and C. tarsalis in four counties in South-Central WA and an aggregate of the counties. We used multivariate linear regression models to explore the relationships between temperature, precipitation and WNV seasons. We further examined the relationship between a WNV season’s length and weekly mosquito infection rates. Results differed between counties, but warmer temperatures in the calendar month prior to the start of a WNV season appeared to be strongly linked to delayed season start-times and shorter season durations. Longer seasons were also associated with higher mean-weekly mosquito infection rates. Our research may provide insight into how local environmental conditions influence WNV seasons and how seasons affect mosquito infection rates.