West Nile Virus
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
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.
Letter to Physicians: Report West Nile Virus Infections 2014
Report Dead Birds/Reporte Pajaros Muertos:
1-877-747-2243 or by the
West Nile infected dead birds are indicators of the virus presence.
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
Confirmed West Nile Infections in Los Angeles County*
|Human Infections (Fatalities)
* Does not include the cities of Long Beach and Pasadena. Updates are provided daily if counts change.
Total includes asymptomatic blood donor cases.
Local Epidemiology Reports (WNV Case Totals)
West Nile Virus Epidemiology Report: October
WNV Final Epidemiology Report
WNV Final Epidemiology Reports:
To report potholes or street problems with water accumulation,
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):
contact the appropriate
city utility; if the problem is in an unincorporated area, please contact the
Los Angeles County Department of Public Works.
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
and zoom in on the Los Angeles area.
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Information for Medical Providers and Infection Control Practitioners
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