Disease Control and Environmental Epidemiology -

West Nile Virus Mosquito Sentinel Sites

Each sentinel site file below contains 3 graphs representing the following:

Number of Culex Mosquitoes Collected: These graphs illustrate the number of Culex species mosquitoes collected weekly from each sentinel site.
Infection Rate: Infection rate is an estimate of the number of West Nile virus positive Culex mosquitoes per 1000. This is a statistical calculation based on the number of Culex species mosquito pools tested, the number of pools positive for West Nile virus, and the size of each pool.
Vector Index: Vector index is a measure of infection rate adjusted for Culex mosquito population size within a given area. The value is an estimate of the number of West Nile Virus infected mosquitoes collected at a given sentinel site on any given night. Especially when mosquito populations are small, vector index is more accurate than infection rate as an estimate of human West Nile Virus transmission risk. The data on vector index as a predictor of human transmission is incomplete, but it suggests that a vector index of 0.75 or above is an indicator of high risk for West Nile Virus transmission to humans in the area.