Human Cases
Year-to-date: 126 Counties: 21
There were 39 new WNV positive human cases reported in California this week from the following counties: Butte (2), Fresno (3), Glenn (1), Los Angeles (26), Orange (1), Riverside (1), San Diego (2), Stanislaus (1), Tulare (1), and Yolo (1).
6 WNV-related fatalities have been reported to CDPH this year from 5 jurisdictions: Butte (2), Glenn (1), Kings (1), Los Angeles (1), and Sacramento (1).
126 human cases from 21 counties have tested positive for WNV in 2026.
Dead Birds
Year-to-date: 574 Counties: 23
There were 62 new WNV positive dead birds reported in California this week from the following counties: Alameda (1), Los Angeles (4), Orange (40), Riverside (2), San Bernardino (1), San Diego (3), San Joaquin (2), and Santa Clara (9).
574 dead birds from 23 counties have tested positive for WNV in 2026.
Mosquito Samples
Year-to-date: 3424 Counties: 29
There were 193 new WNV positive mosquito samples reported in California this week from the following counties: Butte (1), Fresno (6), Kern (9), Los Angeles (42), Madera (10), Merced (5), Orange (36), Placer (2), Sacramento (7), San Bernardino (4), San Diego (17), San Joaquin (16), Shasta (1), Stanislaus (22), Tulare (5), and Yolo (10).
3,424 mosquito samples from 29 counties have tested positive for WNV in 2026.
A mosquito sample may contain up to 50 individual mosquitoes.
Sentinel Chickens
Year-to-date: 138 Counties: 10
There were 24 new WNV positive sentinel chickens reported in California this week from the following counties: Butte (5), Contra Costa (1), Lake (2), Los Angeles (11), Sutter (3), Tehama (1), and Yuba (1). This is the first WNV positive sentinel chicken from Contra Costa County this year.
138 sentinel chickens from 10 counties have tested positive for WNV in 2026.
Horses
Year-to-date: 11 Counties: 11
There was 1 new WNV positive horse reported in California this week from Amador County. This is the first indication of WNV from Amador County this year.
11 horses from 11 counties have tested positive for WNV in 2026.