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West Nile Virus 2021 Season Begins

Surveillance for West Nile virus began in California in mid-April. The District protects residents from this mosquito-borne disease with control that targets mosquitoes in the larval stage, mosquito population monitoring, disease surveillance and public education. The laboratory staff conducts surveillance to detect the presence of mosquito-borne disease in three main ways:


Sentinel Chickens

The District manages two sentinel chicken flocks of seven chickens each, in the cities of East Palo Alto and San Mateo. These chickens were transferred from a farm to their District coops on April 15. Chicken blood is tested every two weeks for antibodies to West Nile virus, Saint Louis encephalitis and Western equine encephalitis from April 26 to November 8.


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. All bird species are accepted except water fowl, poultry or pigeons.

To report a dead bird, residents should call the state West Nile virus hotline 1-877-WNV-BIRD (1-877- 968-2473), which opened with live operators on April 12. Online reports can be made at


Mosquito-borne Disease Testing

The District laboratory submitted and passed proficiency panels supplied by Davis Arbovirus Research and Training (DART) for West Nile virus, Saint Louis encephalitis and Western equine encephalitis. The proficiency panels ensure that the testing methods and equipment are capable of detecting these three viruses for the upcoming season and will be acceptable for reporting by the California Department of Public Health (CDPH). Our District will test saliva or ocular samples from dead birds and whole mosquitoes for the presence of these viruses.

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