Human Cases
Year-to-date: 298 Counties: 24
There were 48 new WNV positive human cases reported in California this week from the following counties: Contra Costa (1), Fresno (2), Los Angeles (22), Madera (1), Orange (14), Placer (1), Sacramento (1), San Diego (1), Stanislaus (1), Tulare (3), and Yolo (1). This is the first WNV positive human case from Contra Costa County this year.
19 WNV-related fatalities have been reported to CDPH this year from 8 jurisdictions: Butte (3), Glenn (2), Kings (1), Los Angeles (4), Orange (4), Sacramento (2), Tuolumne (1), and Yolo (2).
298 human cases from 24 counties have tested positive for WNV in 2026.
Dead Birds
Year-to-date: 712 Counties: 25
There were 10 new WNV positive dead birds reported in California this week from the following counties: Alameda (1), Los Angeles (1), Riverside (1), San Diego (4), San Joaquin (1), and Santa Clara (2).
712 dead birds from 25 counties have tested positive for WNV in 2026.
Mosquito Samples
Year-to-date: 3903 Counties: 29
There were 64 new WNV positive mosquito samples reported in California this week from the following counties: Los Angeles (44), Merced (3), San Bernardino (11), San Diego (3), San Joaquin (1), and Tulare (2).
3,903 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: 149 Counties: 11
There were 6 new WNV positive sentinel chickens reported in California last week from the following counties: Calaveras (2), Contra Costa (1), Los Angeles (1), and Tehama (2). This is the first indication of WNV from Calaveras County this year.
149 sentinel chickens from 11 counties have tested positive for WNV in 2026.
Horses
Year-to-date: 15 Counties: 13
There was 1 new WNV positive horse reported in California this week from Shasta County.
15 horses from 13 counties have tested positive for WNV in 2026.