Mosquito vector: Culex
Environmental risk factors:
(1) rural areas with breeding sites for mosquitoes (irrigated fields, swamp, etc)
(2) urban areas with old sewers or canals where the mosquitoes are protected from frosts
(3) other breeding areas (decorative pools, ponds, etc)
(4) ineffective mosquito control
Patient risk factors for exposure:
(1) outdoors in late summer or fall, especially in the evenings
(2) homeless
(3) failure to use mosquito repellant
(4) presence of an outbreak or epidemic
Risk factors for being clinically ill:
(1) age >= 60 years
(2) HIV positive
