Veterinary Public Health

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Veterinary Public Health Program
313 N Figueroa St. Rm 1127
Los Angeles, CA 90012
Tel (213) 288-7060
Fax (213) 481-2375
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West Nile Virus (WNV)



Read about reporting individual dead birds for potential WNV testing.


UPDATE: LA County Veterinary Public Health ceased testing dead birds for West Nile Virus in 2020, but other agencies continue to test them. Learn more about reporting dead birds for WNV testing here.  

What is West Nile virus (WNV)?

  • It is a virus that can infect both people and animals

  • Several species of animals can be infected by WNV, including: birds (especially crows), horses, and some reptiles

  • WNV is an imported disease in the United States. In 1999, the first human and animal cases of WNV were found in New York City

  • It appeared in Los Angeles County for the first time in 2002

    • Since then, WNV infects people and animals every year in Los Angeles County


How is WNV transmitted to people/animals?

  • Both people and animals get infected with WNV through the bite of an infected mosquito


What are symptoms of WNV?

  • In people:

    • Most people infected with WNV do not get sick, in some cases flu-like symptoms may develop (fever, headache, nausea). Very rarely, the virus can infect the brain and cause more severe symptoms.

    • Click here to know more about WNV infections in people.

  • In animals:

    • Birds - Most birds do not get sick from the virus, but may be able to infect mosquitoes that bite them. Crows, ravens and jays may become very ill and die rapidly after infection.

    • Horses - WNV can cause severe neurologic signs in horses, such as: weakness, limb paralysis and death

    • Dogs and cats - Dogs and cats rarely get sick from WNV

    • Other - Tree squirrels can also get sick from the disease


What is the treatment for WNV?

  • There is no specific cure for WNV infection

  • Treatment in people is usually supportive


What should I do to protect myself from WNV?

  • Protect yourself from mosquitoes

    • Wear long-sleeve shirts when mosquitoes are most active, especially at dusk and dawn

    • Empty standing water around your house twice per week to stop mosquitoes from breeding

    • Use mosquito repellent

  • Horse owners should vaccinate their horses


How do I report a dead bird?




Since its first appearance in Los Angeles County in 2003,  WNV has caused infections in animals and humans every year. Monitoring WNV in birds can serve as an early-warning system for human infections:

  • Birds typically begin to die from WNV before cases in humans appear

  • Areas with high numbers of affected crows reflect higher risks of human infection




    2019 WNV dead bird data:

2019 minimap LA County dead birds WNV2017-2019 graph of percentage of dead birds positive for WNV by month through Aug 2019

      (click map for more info)



 Maps of WNV in dead birds - multiple years:

2018 2014 - no map 2010
2017 2013 2009
2016 2012  2008
2015 2011 2007


Data collection is based on passive reporting. Dead bird reports were received by VPH. Until 2013, dead crows were tested in-house; other bird species and squirrels were submitted to a different laboratory for testing. At this time, VPH is no longer able to test individual crows for WNV.




CDFA Guidance for Surveillance and Reporting of Equine West Nile Virus 4.16.2019


WNV in California - California Department of Public Health (CDPH) West Nile virus website


WNV in the US - Centers for Disease Control and Prevention (CDC) West Nile virus page


For physicians - Los Angeles County Department of Public Health - Acute Communicable Disease Control (ACDC) West Nile virus page


Other useful information

Mosquito Control in Los Angeles County


Flyers and brochures

West Nile Virus Palm Card - English, Espaņol

West Nile virus Frequently Asked Questions

Fight the Bite! - California Department of Health Services (Available in: English, Spanish, Vietnamese, Tagalog, Khmer, Hmong)


Last updated: January 25, 2024

Public Health has made reasonable efforts to provide accurate translation. However, no computerized translation is perfect and is not intended to replace traditional translation methods. If questions arise concerning the accuracy of the information, please refer to the English edition of the website, which is the official version.
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