West Nile Virus Is A Growing Threat This Summer In California. What You Need To Know
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The Los Angeles County Department of Public Health (Public Health) has confirmed the first death due to West Nile virus (WNV) for the 2023 season in Los Angeles County. The patient, a resident of the San Fernando Valley area, was hospitalized and died from West Nile virus -associated neuro-invasive disease.

“I send my deepest condolences to the family and friends of this resident who sadly passed away from West Nile virus,” said Muntu Davis, MD, MPH, Los Angeles County Health Officer. “Their death reminds us how important it is to protect ourselves from mosquitoes and prevent them from breeding near our homes. Using mosquito repellent and keeping mosquitoes out of our homes can help prevent West Nile virus. Let’s all work together to keep our homes and neighborhoods mosquito-free for everyone’s safety.”

Humans get West Nile virus through the bite of an infected mosquito. Most mosquitoes do not carry the virus; therefore, most people bitten by a mosquito are not exposed to the virus. Those who do get West Nile virus may experience mild symptoms including fever, muscle aches, and tiredness.

In some cases, especially in persons over 50 years of age and those with chronic medical conditions, such as cancer and diabetes, severe WNV infection can occur and affect the brain and spinal cord causing meningitis, encephalitis, and paralysis. There is no specific treatment for West Nile virus disease and no vaccine to prevent infection.

A total of 19 cases have been documented in Los Angeles County so far this year (excluding Long Beach and Pasadena as cases identified in those cities are reported by their local health departments). Human infections will likely continue to occur through the rest of summer and fall, with the highest number of cases typically arising in this month, September. West Nile virus -infected mosquitoes and dead birds have been identified across Los Angeles County. Public Health monitors cases of West Nile virus infection and collaborates with local vector control agencies to reduce the risk of West Nile virus to humans by promoting prevention and mosquito reduction.

Resident are encouraged to take the following precautions to reduce their risk:

  • Protect yourself: Mosquito repellents can keep mosquitoes from biting you. EPA-registered repellents containing DEET, picaridin, IR3535, 2-undecanone, and oil of lemon eucalyptus are the longest lasting and most effective. They are available as sprays, wipes, and lotions. Consider wearing long-sleeved clothes and pants when outside.
  • Mosquito proof your home: Make sure that your doors and windows have tight-fitting screens to keep out mosquitoes. Repair or replace screens with tears or holes.
  • Reduce mosquitoes: Mosquitoes lay their eggs on standing water.
    • Empty items that hold water inside and outside your home once a week
    • Cover water storage containers such as buckets and rain barrels. If no lid, use wire mesh with holes smaller than an adult mosquito
    • Clear standing water in flower pots, saucers, birdbaths and other outdoor containers
    • Clean and maintain swimming pools, spas and drain water from pool covers
    • Throw away old items in your patio or yard that can hold water, e.g., old car tires and children’s toys
    • Call 2-1-1 or visit www.socalmosquito.org to report persistent problems to your mosquito control district

For more information on West Nile virus, visit publichealth.lacounty.gov/media/westnile. To find a local vector control district, visit http://www.socalmosquito.org.

Other information sources:

Stagnant swimming pools or “green pools” should be reported to the Public Health Environmental Health Bureau at (626) 430-5200, or to a local vector control agency. Dead birds may be reported by calling (877) 968-2473 or online: westnile.ca.gov/report.php

West Nile Virus has been detected in mosquitoes trapped in additional communities in the San Fernando Valley. West Nile Virus is transmitted to people and animals through the bite of an infected mosquito. Residents can do their part to reduce the threat of West Nile Virus by actively taking mosquito control measures: eliminate standing water, properly maintain pools and water features, wear insect repellent outdoors, and report neglected swimming pools to the Greater Los Angeles County Vector Control District. Click here for more information and prevention tips.


West Nile virus infections are on the rise this year in California after a particularly wet winter led to more mosquito reproduction, according to health experts. The state had 55 human cases of the virus as of Aug. 25. Five of them were fatal, according to the California Mosquito-Borne Virus Surveillance and Response Program. That’s more than double the 24 cases that had occurred in 2022 by late August of that year. In total in 2022, there were 207 cases and 15 deaths. Among California’s latest infections, a woman in Orange tested positive for the West Nile virus this week, becoming the first human case in Orange County this year, according to the county Health Care Agency. The Orange resident wasn’t experiencing any symptoms. Last year, there were 11 human infections of the virus and two deaths related to the virus in Orange County. In Los Angeles County, two human cases have been reported so far this year. “West Nile Virus … [recurs] every year during the summer months and continuing into the fall,” Matthew Zahn, deputy health officer for the O.C. Health Care Agency, said in a news release.