In Illinois, West Nile virus is spread by two mosquito species: Culex pipiens and Culex restuans, shown here. The species feed mostly on birds and occasionally mammals, including humans. To control the mosquitoes, abatement districts usually employ public information efforts, source reduction, larval surveillance, and removal of larvae from storm water basins. Active controls such as ULV truck-based applications come into play when the risk of infection is high. (Photo by Katja Schulz via iNaturalist, CC BY 4.0)