Urgent warning as brain-swelling disease surges in multiple Southern California neighborhoods

A dangerous mosquito-borne virus that can cause deadly brain swelling is surging across Orange County — and officials are now sending trucks into one hard-hit city to fight back.

West Nile virus has been detected in mosquito samples from 13 Orange County cities this season, with the number of positive samples more than doubling in just one week, according to the Orange County Mosquito and Vector Control District.

The county has recorded 38 positive mosquito samples so far in its latest testing.

Fullerton has emerged as the hotspot, with near 40% of the cases — reporting 15 positive samples.

The virus has also been found in mosquito samples from Buena Park, Anaheim, Santa Ana, Huntington Beach, Brea, Costa Mesa, Cypress, Garden Grove, Newport Beach, Seal Beach, Stanton and Westminster, according to the district’s surveillance map.

The spike has triggered overnight mosquito control treatments in a 4.5-square-mile section of Fullerton from Thursday through Saturday.

Crews are expected to spray between about 1 a.m. and 5 a.m. each day in an area generally bordered by Valencia Drive, the 91 Freeway, Euclid Street and Raymond Avenue, officials said.

“We only treat when there is an abundance of mosquitoes and the presence of disease,” district officials told KTLA. ” Then that triggers us to go out with our trucks and knock down the adults.”

Residents in the spray zone have already been notified, according to the outlet.

Some people living in the affected area said the mosquito problem has become impossible to ignore.

“There’s been a lot. It’s getting pretty bad,” one Fullerton resident told KTLA. “I don’t go out anymore because you go out and then just mosquitoes, like, right in your face.”

West Nile virus spreads through the bite of an infected mosquito.

Most people who catch the virus never feel sick, according to the Center for Disease Control and Prevention. Others can develop fever, headache, body aches, vomiting, diarrhea or a rash.

In rare cases, the infection can turn severe and cause neurological illnesses such as encephalitis or meningitis — inflammation of the brain or surrounding tissue. Older adults and people with weakened immune systems face the highest risk of serious illness.

The mosquito district is urging residents to dump standing water around their homes, clean bird baths and pet bowls, fix torn window and door screens, and wear insect repellent containing DEET, picaridin, IR3535 or oil of lemon eucalyptus.

Residents can also report neglected pools or unusually heavy mosquito activity to the district for inspection.

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