Surveillance for West Nile virus begins in California each year in April.

The District protects residents from West Nile virus by controlling larval mosquitoes, monitoring larval and adult mosquito populations, testing mosquitoes and dead birds for West Nile virus, and educating the public about mosquito bite prevention.

District staff test dead birds and trapped adult mosquitoes for West Nile virus.

Dead Bird Surveillance

The District collects dead birds that are reported by residents. Dead birds should be in good condition without signs of decay or trauma. Birds except water fowl, poultry or pigeons are collected and tested.

To report a dead bird, residents should call the state West Nile virus hotline at 1-877-WNV-BIRD (1-877- 968-2473), which opens with live operators in mid-April each year. Online reports can be made at westnile.ca.gov.

The District does NOT test for avian influenza ('bird flu') or other diseases - the District testing protocol only tests for West Nile virus, St. Louis encephalitis virus, and Western equine encephalomyelitis virus.

 

Mosquito-borne Disease Testing

The District laboratory tests adult Culex mosquito samples for West Nile virus, St. Louis encephalitis virus, and Western equine encephalomyelitis virus. Samples tested include whole mosquitoes for the presence of these viruses.

 

Page last reviewed: August 6, 2026