First West Nile virus death of the year reported in the US, everything you need to know about the virus, reasons, symptoms and how to stay safe

The Los Angeles County Department of Public Health confirmed Friday(24 October) the first West Nile virus (WNV) death of the year, raising concerns as ongoing drought conditions may increase infection risks in the region. October is the middle of mosquito season in Southern California.

West Nile virus disease is an infection caused by a virus transmitted through mosquito bites. It can range from a mild flu-like illness to severe neurological complications, including encephalitis or meningitis.

The individual, whose identity has not been disclosed, was hospitalized in the San Fernando Valley after developing neurological complications from the mosquito-borne virus. Officials said the patient succumbed to the illness.


So far in 2025, there have been 14 confirmed West Nile virus infections across Los Angeles County, with approximately half occurring in the San Fernando Valley. Historically, LA averages 58 WNV infections annually, with about one death per year, according to county health data.

Understanding West Nile Virus

The Centers for Disease Control and Prevention (CDC) notes that West Nile virus affects roughly 2,000 Americans each year. Symptoms vary widely:

• Mild cases: fever, headache, body aches, vomiting, rash, or diarrhea.
  
• Severe cases: neck stiffness, disorientation, tremors, convulsions, vision loss, muscle weakness, numbness, or paralysis. Severe infections can result in permanent neurological damage or death.
  
• Asymptomatic cases: Some infected individuals experience no symptoms at all.
  

The virus is primarily carried by mosquitoes of the Culex genus, which are widespread throughout Los Angeles County.

Drought may heighten infection risk

The San Fernando Valley has faced prolonged drought and water shortages over the past year, with below-average rainfall contributing to reduced water availability. Recent studies indicate that such conditions can exacerbate the spread of West Nile virus.

A 2025 National Institutes of Health study analyzed data from more than 50,000 mosquito traps and found that while drought decreases overall mosquito populations, it also concentrates infected mosquitoes and birds around limited water sources. This concentration can accelerate virus transmission, potentially increasing human infection rates. Experts warn that with drought conditions expected to persist through a dry La Niña season, local residents may face heightened exposure to the virus.

How to stay safe

Health officials recommend several measures to reduce the risk of contracting West Nile virus:

• Limit outdoor activities during daytime hours when mosquitoes are most active.

• Eliminate standing water around homes, such as in flower pots, buckets, and birdbaths, where mosquitoes breed.
  
• Install window screens and ensure doors are properly sealed.
  
• Wear protective clothing and apply EPA-approved insect repellents when outdoors.
  

Residents are urged to remain vigilant as mosquito season continues through October in Southern California.