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West Nile Virus

WNV is transmitted to humans and animals through a mosquito bite.  Mosquitoes become infected when they feed on infected birds.  Health officials emphasized that the risk of serious illness to humans is low.  Most individuals who are infected with WNV will not experience any illness.  Elderly individuals and those with compromised immune systems are at greatest risk for serious illness.

Individuals can reduce their risk of mosquito-borne diseases by taking these precautions:

  • Avoid spending time outside when mosquitoes are most active, especially at dawn and dusk.
  • When outdoors, wear long pants, long-sleeved shirts and other protective clothing.
  • Apply insect repellent according to label instructions.
  • Make sure that doors and windows have tight fitting screens.  Repair or replace screens that have tears or holes.
  • Eliminate all sources of standing water on your property that can support mosquito breeding.
  • Contact your local mosquito and vector control agency if there is a significant mosquito problem where you live or work.

A comprehensive surveillance program to monitor for WNV in Riverside County has been established by the Department of Environmental Health Vector Control, local mosquito and vector control districts and other state and local agencies. The program includes testing suspect cases in humans and horses, capturing and testing mosquitoes, testing sentinel chickens and evaluating dead birds.

Anyone who becomes ill after exposure to mosquitoes should contact his or her health care provider.  The County of Riverside Department of Public Health Disease Control Office can be reached at (951) 358-5107, for more information about West Nile Virus.  Problems related to mosquito control should be directed to the appropriate Mosquito control office:

  • Riverside County Mosquito Control         951-766-9454
  • Northwest Mosquito and Vector Control   951-340-9792
  • Coachella Valley Mosquito and Vector Control District   760-342-8287

If you are unsure of which agency services your area you may go to: and enter your zip code.

Information about WNV is available on the website established for surveillance in California:   

Dead birds can be reported on that same Web site or by calling toll-free
1-877-WNV-BIRD (1-877-968-2473).

Department of Public Health
Disease Control Branch
Health Administration Building
4065 County Circle Drive, Riverside, CA 92503
(951) 358-5107 | FAX 358-5446 | TDD 358-5124 | Email: