Outbreaks | Equine Disease Communication Center

Updates on current disease outbreaks are listed here as they occur and will include the date listed, disease name, location and current status. Specific premises will not be named but the general location by town, county and state will be listed. When locations, events or horses are at risk they will be listed. Updates will be posted as they are received.

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West Nile Virus

Stanislaus County, CA

Outbreak Identifier: 7591

Alert ID: 5164

August 25, 2026

Confirmed Case(s) - No Quarantine

Source: California Department of Food and Agriculture

Number Confirmed: 1;

Horse 1:
Age: 1; Gender: Filly; Breed: Quarter Horse (QH); Onset of Clinical Signs: 8/10/2026; Clinical Signs: mild ataxia, muscle fasciculations, dull mentation; Confirmation Date: 8/21/2026; Horse Status: Affected And Alive; Vaccination Status: Status Unknown;

Comments: The seventh (7th) equine case of West Nile Virus in California in 2026 was confirmed in Stanislaus County. On Aug. 21, 2026, a 1-year-old Quarter Horse filly with an unknown vaccine history in Stanislaus County displaying neurologic signs was confirmed positive for West Nile Virus. The filly is alive and recovering.;

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