On Dec. 9, California Department of Food and Agriculture (CDFA) officials issued an update on the San Bernardino County equine herpesvirus-1 (EHV-1) outbreak. No new cases were reported, and four of the horses that tested positive for EHV-1 have had two negative tests seven days apart. The other three EHV-1-positive horses have not yet met the testing requirement to be cleared of the disease. Therefore, the entire property remains under quarantine, and CDFA continues to monitor the outbreak.

The outbreak began on Oct. 29 when a 13-year-old Quarter Horse mare displayed neurologic signs and fever and was subsequently euthanized due to the severity of her signs. Postmortem testing confirmed her positive on Nov. 5, and 20 exposed horses on her home premises were quarantined and monitored for the disease.

A second horse, a 22-year-old Paint gelding, subsequently tested positive and was euthanized, with three additional horses on the premises testing positive.

On Nov. 19, CDFA officials confirmed that one of the three horses that tested positive, a 24-year-old Quarter Horse mare, developed severe neurologic signs and was euthanized on Nov. 16