Acute Communicable Disease Control

Contact Information
County of Los Angeles
Department of Public Health
Acute Communicable Disease Control
313 N. Figueroa Street, #212
Los Angeles, CA 90012
Phone: (213) 240-7941
Fax: (213) 482-4856
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Acute Communicable Disease Control
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 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.

- LA County Dead Bird Surveillance and Reporting
- LA County Mosquito Surveillance and Reporting

West Nile Virus and Other Arboviral Diseases Epidemiology Report: October 13, 2016 (10-13-16) Adobe PDF Document

West Nile Virus Frequently Asked Questions English / Spanish Adobe PDF Document

Letter to Physicians: Report West Nile Virus Infections 2016 (8-2-16)  Adobe PDF Document

West Nile Virus Epidemiology Report FINAL REPORT, March 30, 2016 (3-30-15) Adobe PDF Document

Request a speaker: Los Angeles County Department of Public Health Speakers' Bureau

Confirmed West Nile Infections in Los Angeles County*


Human Infections (Fatalities) Equine (Horse)
2016 125(5) 0
2015 300 (24) 0
2014 218 (7) 0
2013 165 (9) 0
2012 174 (6)  1
2011 63 (4) 1
2010 4 0
2009 25 (1) 1
2008 170 (6) 0
* 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 FINAL REPORT, March 30, 2016 (3-30-15) Adobe PDF Document

Los Angeles County WNV Final Epidemiology Reports

2004  /  2005  /  2006  /  2007  /  2008  /  2009  /  2010  /  2011  /  2012  /  2013  /  2014 Adobe PDF Document


Report Dead Birds/Reporte Pajaros Muertos: 1-877-WNV-BIRD (1-877-968-2473) or by the Internet.

Bird Surveillance: 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 documentation of WNV positive dead birds have been ongoing. Please report dead birds to the State of California's West Nile Virus program at 1-877-WNV-BIRD (1-877-968-2473) or by the Internet.  For the most up-to-date map of WNV positive activity, click here.

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) 933-5321
San Gabriel Valley
(626) 814-9466
City of Pasadena
(626) 744-6005
Orange County
(714) 971-2421

Mosquito Surveillance: 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.  For the most up-to-date map of WNV positive activity, click here.

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.

Latest News and Updates

Information for Medical Providers and Infection Control Practitioners

Additional Resources

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