Los Angeles County has begun targeted mosquito spraying in La Puente as West Nile virus infections climb to 100 this year, with 94 people hospitalised and five deaths recorded, health officials said.
Vector-control crews carried out the overnight operation on Wednesday, targeting mosquitoes capable of transmitting the virus. Cases have been reported across the county, from the South Bay and East Los Angeles to the San Fernando Valley.
The latest figures, updated by the Los Angeles County Department of Public Health on 17 September, represent more than four times the number of infections recorded during the whole of 2025. That year, 22 infections, 18 hospitalisations and two deaths were reported, excluding cases from Long Beach and Pasadena.
West Nile virus cases rise in Los Angeles County
Anais Medina Diaz, communications director for vector control, said persistently warm nights were helping to fuel mosquito activity and increase the risk of disease transmission.
“It stayed warm. Stays warm overnight. There’s a lot of mosquito activity, disease activity,” she said.
The Greater Los Angeles County Vector Control District says surveillance in 2026 has identified hundreds of mosquito samples carrying West Nile virus, as well as infected dead birds in communities across the region.
Large-scale spraying is generally reserved for periods of unusually high mosquito numbers, elevated virus activity or other public-health emergencies. The treatments are intended to reduce adult mosquito populations and slow transmission.
Residents in La Puente said the increase in mosquito activity had become difficult to ignore. One woman, who identified herself as Bree, described the bites as intensely irritating, while another resident said she was particularly worried because she is pregnant.
“I’m pregnant and I’m trying to avoid all the mosquitoes I can,” she said.
Symptoms of West Nile virus
Most people infected with West Nile virus do not develop serious illness, but severe cases can cause fever, confusion, muscle weakness and neurological complications, including inflammation of the brain or paralysis.
Dr Dawn Terashita, a public-health and internal-medicine specialist, said the most serious infections could lead to death. There is currently no vaccine or specific treatment for West Nile virus.
Los Angeles County officials are urging people to reduce exposure by using insect repellent, wearing long sleeves outdoors and removing standing water from gardens and other areas around their homes.
Mosquitoes are most active around dawn and dusk, and older people and those with underlying health conditions face a greater risk of severe disease.
