West Nile virus activity tops last year across Greater Los Angeles, vector district says

The Greater Los Angeles County Vector Control District on Monday, Sept. 28, 2026, alerted residents to heightened West Nile virus activity across Los Angeles County, saying virus-positive mosquito samples and dead birds have surpassed last year’s levels and are trending above the five-year average.

So far this year, the district has detected 384 WNV-positive mosquito samples and 78 WNV-positive dead birds, compared with 104 positive mosquito samples and two positive dead birds at this time last year, it said. The Los Angeles County Department of Public Health has reported over 100 human cases and five deaths, according to the district.

The district said native Culex mosquitoes, which can transmit the virus and are most active from dusk to dawn, remain below the five-year average in abundance within the district, but virus activity is significantly elevated.

“West Nile virus is cyclical, and the level of activity we see can look different each year,” said Steve Vetrone, the district’s assistant general manager of vector management services. “This year, we have seen increased disease activity across the region, with activity beginning earlier than usual.” He said an extremely mild winter, with rainfall interspersed with unusually warm weather earlier in the year, was among the environmental factors behind the conditions.

“After seeing increased activity early in the season, we stepped up inspection and control efforts along with mosquito monitoring, and public outreach,” Vetrone said. “The control efforts have helped keep WNV transmitting Culex mosquito populations low.” The district said it mobilized staff across its Operations, Scientific-Technical, and Communications departments.

With no human vaccine currently available, the district urged residents to use insect repellent containing at least 15% DEET, Picaridin, IR3535, or Oil of Lemon Eucalyptus; wear loose-fitting, long-sleeved shirts and pants; remove standing water around the home; and report neglected or green swimming pools to their local vector control agency. Dead birds can be reported to the California Department of Public Health at westnile.ca.gov or by calling 1-877-WNV-BIRD; the district can be reached at 562-944-9656.

There is no cure for West Nile virus, according to the district, which said one in five people infected will show symptoms and one in 150 will require hospitalization.

See something we should correct? Read our corrections policy.