West Nile virus (WNV) is a disease transmitted to humans, birds, horses, and other animals, by infected mosquitoes. Mosquitoes get the disease from feeding on infected birds and can later pass it on when they bite animals or humans.
WNV is established in San Diego County and can be found in all 58 counties in California! The virus was first isolated in the West Nile district of a Northern Province in Uganda in 1937. It was first detected in the United States in New York City in 1999. From there, the virus spread westward, arriving in California in 2003. West Nile virus is now the most prevalent mosquito-borne disease in the United States.
The Vector Control Program protects communities and the environment by controlling mosquitoes that can transmit diseases to humans.
Vector Control Program staff monitor WNV by trapping, pooling, and testing mosquitoes and by testing sentinel chickens and dead birds.