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Disease Alerts

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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Equine Herpesvirus- Neurologic
San Mateo County, CA
Outbreak Identifier: 5069
Alert ID: 2434
February 23, 2022
Outbreak Update

California Department of Food and Agriculture

Number Confirmed: 23;
Number Exposed: 300;
Gender: Mare;
Clinical Signs: Fever; Confirmation Date: 2/22/2022; Horse Status: Affected And Alive;
Gender: Mare; Onset of Clinical Signs: 2/17/2022;
Clinical Signs: Fever; Confirmation Date: 2/22/2022; Horse Status: Affected And Alive;
Age: 22; Gender: Gelding; Breed: Quarter Horse (QH); Onset of Clinical Signs: 2/16/2022;
Clinical Signs: Fever; Confirmation Date: 2/22/2022; Horse Status: Affected And Alive;
Age: 27; Gender: Gelding; Breed: Quarter Horse (QH); Onset of Clinical Signs: 2/15/2022;
Clinical Signs: Fever; Confirmation Date: 2/22/2022; Horse Status: Affected And Alive;
Notes: Update: 2/23/22: Previous Alert ID: 2405, 2406, 2408, 2410, 2415, 2423, 2426: Four (4) additional horses from the index premises displaying fever only with no neurological signs were confirmed positive for EHV-1 on February 22nd, and have been isolated at the index premises. To date, two (2) EHM cases (EHV-1 positive with neurologic signs) and twenty-one (21) EHV-1 febrile only cases have been confirmed. The quarantine will be released when all positive horses have had two (2) consecutive negative tests seven (7) days apart. CDFA continues to actively monitor the situation.;
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