Impacts of Climate Variability on West Nile Virus Infections in Central North Georgia, USA

More than 35,000 West Nile Virus (WNV) disease cases have been reported to CDC since 1999 in the United States. Just recently in 2012, 48 states have reported WNV infections in people, birds, or mosquitoes to CDC. Georgia, specifically Atlanta area, has been a hotspot of WNV incidence in 2012 with 78 WNV human cases, 6 deaths and 113 WNV positive mosquitos reported by Georgia Department of Public Health. Transmission of vector-borne diseases is influenced by a wide range of environmental factors and climatic variability is an important driver of inter-annual WNV transmission risk. In this study, effect of meteorological variation on Vector Index, which is an estimate for the average number of infectious mosquito per trap night and reflects risk of human disease, was explored for the central north part of the State of Georgia. The meteorological data was downloaded from National Weather Service, Climate prediction Center and mosquito data was obtained from the Georgia Department of Community Health. Cross correlation function (CCF) was applied to consider the impacts of inter-annual variability of mean weekly precipitation, temperature, actual and potential evapotranspiration (AET and PET), available moisture in surface layer and drought on Vector Index from 2002 to 2011. Results showed that mosquito abundance was highly correlated with warmer temperature and high AET and PET in the study area. Also, dry condition in spring followed by above average temperature and below average precipitation was associated with high risk of infection and human disease with WNV in summer. We suggest that drought condition is linked closely to the relative risk of WNV infection and this can help enhance the ability of predicting WNV outbreaks.