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West Nile Virus

West Nile virus (WNV) is an infection of birds that is transmitted by mosquitoes. Occasionally, humans and animals are infected when bitten by an infected mosquito. West Nile virus tends to be seasonal, beginning in the early summer and continuing through fall. In humans, most infections, 70-80% infections result in no symptoms. About 20-30% of persons who are infected will have symptoms that may include fever, headache, rash, nausea, vomiting and body ache. Less than 1% of persons will have severe illness and while rare, it can be fatal for the elderly and people with compromised immune systems.

What You Can Do:

  • Protect your home & garden from mosquito breeding and use insect repellents when outside.
  • Report dead birds and squirrels to monitor West Nile Virus activity. To report a dead bird or squirrel in California, complete a web-based form or call 1-877-968-2473.
  • Report neglected (green) swimming pools to Contra Costa Mosquito & Vector Control, complete a web-based report or call 925-771-6196. Free mosquitofish can be requested. Neglected pools, ponds, and troughs produce mosquitoes putting you and your family at high risk for West Nile virus.

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