Orange County’s first West Nile Virus (WNV) positive mosquito samples of the season were identified last week in Fullerton through routine trapping and testing by the Orange County Mosquito and Vector Control District (OCMVCD).

NV positive mosquito samples have been identified in Los Angeles, San Bernardino and Riverside County this year.

St. Louis encephalitis virus (SLEV) was detected in five mosquito pools in Riverside County last week for the first time in 2021.

One human case of WNV was reported two weeks ago from Los Angeles County.

No human infections of WNV or SLEV have been identified so far this season in Orange County.

West Nile virus (WNV) is the leading cause of mosquito-borne disease in the continental United States, according to the CDC.  It is most commonly spread to people by the bite of an infected mosquito. Cases of WNV occur during mosquito season, which starts in the summer and continues through fall.

There are no vaccines to prevent or medications to treat WNV in people. Fortunately, most people infected with WNV do not feel sick. About 1 in 5 people who are infected develop a fever and other symptoms. About 1 out of 150 infected people develop a serious, sometimes fatal, illness.

You can reduce your risk of WNV by using insect repellent and wearing long-sleeved shirts and long pants to prevent mosquito bites.