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2021 West Nile Virus Activity

This map details mosquitoes, dead birds, chickens, and horses that have tested positive for West Nile virus. You can zoom in and out of the map and click on the placemarkers to get a detailed description of the date the positive activity was confirmed and the approximate location.

May contain: cutlery, spoon, chart, and plot

 For information regarding human cases, please click here.


Mosquito Samples: 8
nDate CollectedCityCross StreetsSpecies
16/29/21ByronWestern Farms Ranch RdCulex tarsalis
27/13/21BrentwoodOrwood Rd x Levee RdCulex tarsalis
38/10/21Discovery BayCherry Hills DrCulex tarsalis
48/10/21BrentwoodFletcher LnCulex tarsalis
58/30/21Discovery BayCherry Hills DrCulex pipiens
69/8/21BrentwoodHolland TractCulex tarsalis
79/8/21BrentwoodOrwood Rd x Levee RdCulex tarsalis
89/20/21OakleyMain St x Oakley RdCulex tarsalis
Dead Birds: 3
nDate ReportedCityCross StreetsSpecies
18/21/21BrentwoodSand Creek Rd x Minnesota AveCA Scrub Jay
29/20/21San PabloBirmingham Dr x Groom DrAmerican Crow
39/25/21MartinezMorello Ave x Midhill RdAmerican Crow


Sentinel Chicken Flocks: 0

Note: Chickens do not die from West Nile virus. They develop antibodies to the virus which is detected in their blood.


Horses: 0
nDate ReportedCityDead/Euthanized