LA County reports highest number of West Nile virus cases since 2017

Los Angeles County health officials on Monday reported that the county has recorded 100 West Nile virus cases this year, marking the highest number in nearly a decade.

In a news release, the Los Angeles County Department of Public Health reported that the last time the county saw numbers so high was in 2017, when 268 cases were reported for the entire season. 

DPH officials say that five people have died from the virus so far this year, and that "almost all [of the patients] have had severe illness."

"This is expected because milder infections often go undiagnosed and are not usually reported," the release said. "These severe illnesses affect the brain or spinal cord, and almost all patients have needed hospital care."

Related: Orange County officials warn of "five-alarm year" for mosquitoes and West Nile virus

Officials said the 100 cases are the most seen this early in mosquito season in the last nine years and urged locals to use repellents, remove standing water from around their homes, constantly maintain pools or fountains, and make sure that screens and doors are fitted with properly secured screens with no holes or tears that the bugs can get through. 

The release further noted that West Nile virus is the most common mosquito-borne disease that affects Los Angeles County, and that the virus is endemic to the region. Mosquito season typically runs from June through November, but some Southern California officials said that the season got to an early start in 2026 due to a series of storms earlier in the year that mixed high heat with humid conditions. 

"West Nile virus activity is higher than we typically see, and our teams are actively responding with enhanced surveillance, targeted mosquito control treatments, disease investigations, and increased community outreach and education," said a statement from Jason Farned, the San Gabriel Valley Mosquito District manager.

According to DPH, West Nile virus is transmitted through the bites of infected mosquitoes. Most people who become infected don't experience symptoms, but "about 1 in 5 people who are infected develop a fever with other symptoms." Common symptoms of West Nile virus include headache, body aches, joint pain, vomiting, diarrhea and rash.