Fig. 1: Schematic of the mosquito life cycle and control measures. The development of immature mosquitoes from eggs to larvae to pupae occurs in standing water. These stages of the mosquito life cycle can be disrupted by eliminating standing water where possible and by applying larvicides to water bodies containing larvae. When the pupae develop into winged adults, mosquitoes acquire West Nile virus by biting infected birds. The incubation period in mosquitoes is about 2–3 weeks. An infected mosquito might then bite a person, passing the virus on. Many bird species act as reservoirs for the virus, and many mosquito species are involved in passing the infection from bird to bird, or from bird to human, or both. Populations of adult mosquitoes can be controlled by spraying adulticides. Individuals can reduce their exposure to mosquitoes by undertaking personal protective measures. Photo: Chesley Sheppard