All four infected persons were hospitalized from late July through August but are recovering.

The first cases of West Nile virus this year have been recorded in Los Angeles County, with four people hospitalized between July and August, officials said.

The Los Angeles County Department of Public Health on Wednesday announced that patients from the Antelope Valley, San Fernando and central Los Angeles were infected with the virus, hospitalized and are now recovering.

"The first human cases of West Nile virus are an important reminder that we all need to take steps to prevent mosquito bites and mosquito breeding," said Dr. Muntu Davis, L.A. County health officer, in a statement.

"Mosquitoes thrive in hot weather, increasing the risk of bites and mosquito-borne diseases."

West Nile is spread by the bite of infected mosquitoes. Those who have contracted the virus may suffer from a variety of symptoms, including fever, headache, nausea, body aches and a mild skin rash.

The virus can attack the nervous system and lead to meningitis, encephalitis, paralysis and, in rare cases, even death.

Risk is acute in adults 50 years of age or older and for those with chronic health conditions.

It is believed the mosquitoes carrying the virus are in L.A. County, though not all are carriers, according to health officials.

Davis encouraged residents to use insect repellent, get rid of standing water around their homes and install or repair windows to reduce exposure to mosquitoes.

Environmental Protection Agency-registered sprays contain DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone and are proven safe and effective, even for pregnant and breastfeeding women, according to health officials.

Also avoiding areas at dawn or dusk when mosquitoes congregate is key to avoid getting bitten.

An individual should consider wearing long-sleeved shirts and long pants when venturing to an area known for mosquitoes.

Mosquitoes tend to lay eggs in places with standing water.

The health department recommends emptying and scrubbing places where water accumulates, including tires, buckets, pet bowls, planters and rain barrels.

Birdbaths and wading pools should be cleaned weekly, while pools should be cleaned and chlorinated regularly.

The health department said over the last five years, L.A. County (minus Pasadena and Long Beach, which report to their own agencies) has averaged about 56 West Nile virus cases per year. The number of infected people, however, is expected to be much higher since most impacted individuals suffer mild symptoms and don't file a report with the county, according to the health department.

The Greater Los Angeles County Vector Control District reported 132 cases last year, with Northridge (eight), Lake Balboa (seven) and Porter Ranch (seven) producing the most recorded infections. There were two deaths in the county and 12 in the state in 2024, according to state figures.

About three-quarters of reported cases in L.A. County have had severe disease and approximately 10% of patients with severe West Nile virus die from complications.

There is no specific treatment for West Nile virus disease and no vaccine to prevent infection.

"Detecting West Nile virus in our district is a reminder that this virus has been present in California -- and right here in our community -- for over 20 years," Brenna Bates-Grubb, community outreach specialist for the Antelope Valley Mosquito and Vector Control District, said in a statement.

"It's part of our local environment and continues to reappear year after year," she added. "With the recent rains and more in the forecast, conditions are ideal for mosquitoes to breed."

L.A. County confirms first 4 West Nile virus cases of the summer in local residents