What is West Nile Virus?

West Nile Virus (WNV) is a potentially serious viral illness. It is common in Africa, west Asia, the Middle East, and, since 1999, North America. WNV has been found in mosquitoes, birds, animals and humans in every U.S. state except Hawaii and Alaska. It is a seasonal epidemic that flares up in summer and continues into fall. Most humans infected with WNV have relatively mild symptoms or none at all. However, some WNV infections may result in serious illness.

How WNV IS Spread to Humans?

WNV virus is transmitted to humans and animals through a mosquito bite. Mosquitos become infected when they feed on infected birds. Human-to-human transmission of WNV does not occur. However, human WNV infections have been associated with blood transfusions and organ transplants.

Control Activities in Alameda County

West Nile Virus has been detected in 51 of California’s 58 counties (as of 9/26/07). Alameda County is taking steps to limit risks to residents. Alameda County’s Mosquito Abatement program includes: monitoring ponds and other possible mosquito breeding sites, trapping to detect high numbers of mosquitoes, treating sewer catch basins to prevent breeding, collecting birds for testing, and educating residents and owners about removing standing water from private property and avoiding mosquito bites.