The number of people confirmed to be infected with West Nile virus in the San Joaquin Valley is creeping higher, wrestling in California’s first death from the mosquito-borne virus in Kings County.

The death was announced Aug. 3 by Rose Mary Rahn, director of the Kings County Department of Public Health. No details were released about the victim’s place of residence, age or gender.

“This loss underscores the serious risks associated with WNV,” Rahn said in a prepared statement. “It is still early in the WNV season, and we continue to urge all residents to take preventative measures against mosquito bites, including eliminating standing water where mosquitoes can breed.”

So far this summer, three confirmed human infections of West Nile have occurred in Kings County, including the fatality. The county’s first confirmed case was reported on July 20.

So far, at least eight confirmed cases of West Nile virus have been reported in the Valley. In addition to the three in Kings County, three cases have been confirmed in Tulare County and one each in Madera and Fresno counties, all since mid-July.

The California Department of Public Health reports that other California cases have been reported in Butte, Los Angeles, Sacramento, San Diego and Santa Clara counties.

As part of a West Nile surveillance program, counties and the state trap mosquitoes, chickens and dead birds to monitor the spread of the virus. As of July 31, the virus has been identified in 1,464 mosquito samples, 288 dead birds, 12 chickens and three horses in addition to the human cases statewide.

In 2025, the California Department of Public Health confirmed 117 human cases of West Nile virus in the state – the third-lowest total in more than 20 years – of which 11 proved fatal.

Health officials report that most people who become infected by West Nile experience no symptoms at all. About 20% have mild symptoms that can include fever, headache, body aches, nausea and vomiting.

But for some people, including the elderly or those with compromised immune systems, the virus can cause severe neurological illness and death.

West Nile virus is the leading cause of mosquito-borne illness in the U.S. The U.S. Centers for Disease Control estimates that about 2,000 people are diagnosed each year, but most cases are believed to go unreported because the victims either experience no symptoms or think their symptoms are related to some other cause.

More than 1,300 people each year develop a serious case of West Nile affecting the central nervous system, with about 130 deaths per year. There are no licensed vaccines or medicines to prevent or treat West Nile disease in humans, the CDC reports.

Health officials warn that to protect against West Nile or other illnesses carried by mosquitos, residents can:

  • Use an insect repellent containing DEET, picaridin, oil of lemon, eucalyptus or Insect Repellant 3535 to keep mosquitoes from biting.
  • Wear long sleeves and long pants, as well as using mosquito repellent, during the early morning and evening hours when mosquitoes are most active.
  • Make sure that screen doors and window screens are tight-fitting to keep mosquitoes outside, and to repair damaged or torn screens.
  • Eliminate or drain sources of standing water where mosquitoes can lay their eggs. This includes flower pots, buckets, old car tires and other containers. Swimming pools that are not properly maintained and have green or stagnant water can also be a breeding ground for mosquitoes.

Tim Sheehan is the Health Care Reporting Fellow at the nonprofit Central Valley Journalism Collaborative. The fellowship is supported by a grant from the Fresno State Institute for Media and Public Trust. Contact Sheehan at tim@cvlocaljournalism.org