West Nile Virus Activity Surges in US and Canada in 2026
Across the United States and Canada, public‑health agencies are reporting a sharp rise in West Nile virus activity in 2026. Utah health officials said 296 mosquito pools tested positive for the virus, a seven‑fold increase from the previous season, and the state recorded its first human case of the year in Salt Lake County. In Orange County, California, mosquito traps in 16 cities have yielded 206 positive samples, the highest count on record, though no human infections have been confirmed.
In California’s Santa Clara County, two human cases were confirmed, but officials noted the infections were likely acquired while the patients were traveling, not locally. The county did, however, detect two positive mosquito pools. Similar findings of positive mosquito pools without human cases were reported in Niagara Region, Ontario, and Windsor‑Essex County, Ontario, where a crow also tested positive. In the United States, a dead crow in Menlo Park, California, tested positive, bringing the local dead‑crow count to three. Galveston County, Texas, confirmed a neuroinvasive human case that appears to have been contracted outside the county. Toronto, Ontario, announced its first human case of the year, adding to the growing list of confirmed infections across the continent.
Entities: Dr. Mehdi Aloosh · Ontario · Orange County Mosquito and Vector Control District · Santa Clara County Health Department · Toronto Public Health · Utah Department of Health · West Nile virus · Windsor Essex County Health Unit
Claims
What the coverage asserts, and how well corroborated each claim is across sources.
- [○ 1 SOURCE] Utah reported 296 mosquito pools testing positive for West Nile virus in 2026, up from 39 the previous season. (Utah health officials)
- [○ 1 SOURCE] Santa Clara County detected two positive mosquito pools for West Nile virus in 2026. (Santa Clara County health officials)
- [○ 1 SOURCE] Windsor‑Essex County Health Unit reported a crow and a second mosquito pool testing positive for West Nile virus, with no human cases. (Windsor‑Essex County Health Unit)
- [○ 1 SOURCE] Santa Clara County confirmed two human West Nile virus cases in 2026 but could not determine where the infections were acquired. (Santa Clara County health officials)
- [○ 1 SOURCE] A dead crow in Menlo Park, California tested positive for West Nile virus, bringing the local total to three dead crows. (San Mateo County Mosquito and Vector Control District)
- [○ 1 SOURCE] Niagara Region reported its first positive mosquito pool for West Nile virus in 2026, with no human cases identified. (Niagara Region Public Health)
- [○ 1 SOURCE] Galveston County confirmed a neuroinvasive West Nile virus case in 2026, likely acquired outside the county. (Galveston County Health District)
- [● 2 SOURCES] Toronto Public Health confirmed the city’s first human West Nile virus case of 2026. (Toronto Public Health)