Department of Public Health - Acute Communicable Disease Control

West Nile Virus
Click Image for West Nile virus transmission cycle<

West Nile virus (WNV) causes a potentially serious illness related to Japanese Encephalitis (JE) and Saint Louis encephalitis (SLE). The virus survives in nature in birds and is transmitted by mosquitoes that feed on infected birds (click on image). When humans and other mammals, such as horses, are bitten by infected mosquitoes they may also become infected with WNV. Most persons who become infected with the virus will not become ill. However, for the small proportion who do become sick, symptoms can include fever, headache, rash, muscle weakness, and nausea and vomiting. A smaller proportion may develop neurological symptoms such as limb paralysis, tremors, and altered mental status.

Before 1999,when it was detected in New York City, WNV was found in Africa, Asia, Europe, Middle East, and Australia. Since then, the virus has spread throughout the United States as well as other parts of North America. In 2006, 4269 confirmed human WNV cases were reported nationally to the Centers for Disease Control and Prevention (CDC); California (CA) reported 278 cases.

Report Dead Birds/Reporte Pajaros Muertos: 1-877-747-2243 or by the Internet.

Bird Maps: West Nile infected dead birds are indicators of the virus presence. In 2004, viral positive dead birds were recovered from nearly all areas of Los Angeles County. Since then, collection, testing and site posting of viral positive dead birds have been ongoing. For current bird maps and information on how to collect dead birds for disease testing visit Veterinary Public Health. 2008 Map

Confirmed West Nile Cases, 2008

	Human Cases (Fatalities)	Equine (Horse) Cases
Los Angeles County *	162* (5)	0

* Does not include the cities of Long Beach and Pasadena..

Updates are provided daily if case counts change.

Reporting Mosquito Breeding Sites and Areas With Water Accumulation

Acute Communicable Disease Control is responsible for monitoring and addressing human health problems in Los Angeles County, but is not directly involved with mosquito control activities. This important action is under the control of the county’s five independent mosquito control (abatement) districts. Beyond our county, the Health Departments of Long Beach and Pasadena also operate their own mosquito control programs.

To report a potential mosquito breeding situation, please contact the appropriate Mosquito Abatement District or city public health department (locate your vector control districts by zip code):

Antelope Valley (661) 942-2917	Greater Los Angeles (562) 944-9656	L.A. County West (310) 915-7370	City of Long Beach (562) 570-4132
Compton Creek (310) 639-7375	San Gabriel Valley (626) 814-9466	City of Pasadena (626) 744-6005	Orange County Vector Control

To report potholes or street problems with water accumulation, contact the appropriate city utility; if the problem is in an unincorporated area, please contact the Los Angeles County Department of Public Works.

Mosquito Maps: Like infected dead birds, mosquito surveillance programs operated by Mosquito Abatement Districts statewide help identify the WNV transmission cycle before human cases occur. Mosquito pools comprising of 10 to 50 mosquitoes are trapped and tested for the presence of several mosquito-borne viruses including WNV. To see a map of the locations of recent WNV-positive mosquito pools, visit CalSurv and zoom in on the Los Angeles area.

Special Studies