Horse in Santa Ynez Valley infected with West Nile virus by a mosquito in August

SANTA BARBARA COUNTY, Calif. (KEYT) - A horse in the Santa Ynez Valley tested positive for mosquito-borne West Nile virus in late August. It's the first discovery of the virus in Santa Barbara County since 2020, according to a statement released Sunday by the county's Mosquito and Vector Management District.

The 5-year-old horse had not been vaccinated against West Nile virus since 2022. It has since recovered from the disease. Mosquito trap surveys were conducted near incident site in early September and the mosquitoes all tested negative, per the Mosquito and Vector Management District.

West Nile virus is most commonly transmitted in humans and horses through mosquito bites, according to the Centers for Disease Control, which notes that about 2,000 people get the disease each year in the United States. Horses make up 96.9% of reported non-human cases, per UC Davis.

The county's Mosquito and Vector Management District recommends horse owners stay up to date with their vaccinations. Residents are also urged to report dead birds to the California Department of Public Health, as wild birds are the main source of West Nile virus for mosquitoes.

The CDC says most people who get the virus do not develop symptoms. Some develop a mild illness that includes flu-like symptoms such as fever, headache, vomiting, diarrhea or rash. A small fraction of cases can lead to severe complications like encephalitis, meningitis, or even death.

West Nile virus cases in people across the United States were up more than 40% year-over-year as of early September, per Mike Stobbe of the Associated Press.