Los Angeles County West Nile Cases Surge to 135 as the county continues through an unusually active mosquito-borne disease season. The Los Angeles County Department of Public Health now lists 135 West Nile virus infections for 2026, including 130 hospitalizations and five deaths. The total has risen sharply since county officials announced 100 cases in September, showing that transmission is continuing even as Southern California moves into fall.
Cases Have Climbed From 100 to 135
The Los Angeles County Department of Public Health currently reports 135 infections, 130 hospitalizations and five deaths. That is up substantially from the 100 cases announced by the county on September 21. The current numbers also stand far above 2025, when Los Angeles County recorded 22 infections for the entire year. The high hospitalization count does not mean nearly everyone infected with West Nile virus becomes seriously ill. Mild and symptom-free infections are often never diagnosed, so official case counts tend to capture the more serious end of the disease spectrum.
Health Officials Had Already Warned of an Unusual Season
When Los Angeles County reached 100 cases in September, health officials said the county had not seen that many infections this early in the season in nearly a decade. The September 21 Public Health announcement also reported 94 hospitalizations and five deaths at that time. The latest total of 135 cases means another 35 infections have since been added to the county’s surveillance data. West Nile virus activity can vary dramatically from year to year depending on weather, mosquito populations, bird infections and other environmental conditions.
Most Infections Never Make It Into the Official Count
West Nile virus is primarily spread through the bite of an infected mosquito. Mosquitoes become infected after feeding on infected birds and can later pass the virus to people and other animals. Most infected people never develop symptoms. Some experience fever, headache, body aches, fatigue or rash, while a much smaller percentage develop serious neurological disease such as meningitis or encephalitis. Older adults and people with certain underlying medical conditions face a greater risk of severe illness. Because so many infections cause few or no symptoms, the 135 confirmed cases represent only the portion of infections that were identified and reported.
Mosquito Activity Remains Widespread Around Los Angeles
The Greater Los Angeles County Vector Control District continues to track West Nile-positive mosquito samples across its service area. Positive mosquito activity has been reported in numerous communities throughout Greater Los Angeles, showing that the virus is not limited to one neighborhood or part of the county. Mosquito surveillance helps vector-control officials identify areas of activity before human infections are necessarily reported, while dead-bird surveillance provides another way to track the movement of West Nile virus through local bird populations.
Standing Water Around Homes Still Matters
Even during a large regional West Nile season, mosquito control begins at the property level. Buckets, plant saucers, birdbaths, toys, clogged gutters and other containers can collect enough water for mosquitoes to develop. Southern California’s warm fall weather can allow mosquitoes to remain active long after summer officially ends. Residents should continue dumping standing water, repairing damaged screens and using an EPA-registered insect repellent when appropriate. PestMarket’s Mosquito Control Guide covers additional ways to identify breeding sites and reduce mosquito activity around homes.
This Is Not Yet the Worst West Nile Year LA Has Seen
Los Angeles County has experienced higher annual totals in previous years, so 135 cases does not make 2026 the county’s worst West Nile season on record. What makes the current season notable is how quickly cases accumulated and how many severe cases have already required hospitalization. Surveillance totals can also continue to change after the weather begins cooling because there is often a delay between infection, illness, testing and reporting.
Mosquito Season Is Not Over Yet
October may feel like the end of mosquito season, but Southern California does not experience the abrupt temperature drop seen in colder parts of the country. Mosquitoes can remain active while conditions stay favorable, which means residents should not stop taking precautions simply because summer has ended. The climb from 100 to 135 reported infections reinforces that point. For Los Angeles County residents, removing standing water, limiting mosquito exposure and following local vector-control updates remain important as the 2026 season continues.