Overview
- Public-health data show an unusually early and broad rise in West Nile activity in late July 2026 with the CDC reporting 113 human cases so far this year and multiple localities recording sharp increases in infected mosquitoes and dead birds.
- Local agencies reported recent hot spots that include more than 200 positive mosquito samples in Davis County, Utah and 206 positive mosquitoes in Orange County, California, plus first mosquito positives this season in Wauwatosa, Wisconsin.
- Santa Clara County announced its first two human cases of 2026 and Toronto confirmed the city’s first human case this year, though Santa Clara officials say recent patients traveled domestically so the exact exposure sites remain unclear.
- Vector-control responses now emphasize stepped-up trapping, pooled mosquito testing and targeted larvicide or adulticide actions, and officials are urging residents to use repellent, remove standing water, fix screens, and avoid outdoor activity at dusk and dawn.
- West Nile circulates mainly between birds and Culex mosquitoes so entomological signals often precede human peaks and public-health experts warn older adults and immunocompromised people face the highest risk of severe disease.