Mosquitoes trapped in Hamilton County tested positive for West Nile virus, the first detection of the season in the jurisdiction that includes Montgomery, Blue Ash and Sycamore Township.
Hamilton County Public Health (HCPH) learned of the positive test result on Wednesday, Aug. 26, and announced it publicly on Thursday, Aug. 27. The mosquitoes were trapped in Green Township on July 30 and sent to the Ohio Department of Health for testing.
No human cases have been reported.
HCPH's jurisdiction covers all of Hamilton County except Cincinnati, Springdale and Norwood. That means the agency's mosquito surveillance and response efforts extend across Montgomery, Blue Ash and Sycamore Township.
Larvicide treatment scheduled
Environmental health specialists were scheduled to begin treating standing water in the Green Township area with larvicide on Thursday, Aug. 27, according to Fox 19. Specialists are also surveilling the area and distributing educational materials to residents.
In 2025, Hamilton County recorded three positive mosquito samples and one locally acquired human case of West Nile virus, confirmed by the U.S. Centers for Disease Control and Prevention (CDC) in late September.
How residents can protect themselves
HCPH is urging property owners to follow its "drain, dunk, protect" method:
- Drain standing water from pools, birdbaths, toys, open containers, wheelbarrows, old tires and gutters.
- Dunk: buy larvicide products to kill mosquito larvae in standing water that cannot be drained.
- Protect: avoid being outdoors at dusk and dawn, especially in humid or wooded areas. Wear light-colored, loose-fitting clothing and apply mosquito repellent according to product instructions.
West Nile virus symptoms
West Nile virus affects the central nervous system and spreads to humans through the bite of an infected mosquito. Mild cases produce flu-like symptoms: fever, headaches, body aches, joint pain, vomiting, diarrhea or rash. Most people with mild illness recover completely, though fatigue and weakness can linger for weeks or months.
People who experience severe symptoms should see a doctor immediately. Serious complications include meningitis, encephalitis and acute flaccid myelitis.
Reporting mosquito problems
Residents who notice high mosquito activity or standing water on an abandoned property or in a neglected pool can file a complaint online at hamiltoncountyhealth.org or call HCPH at (513) 946-7000. The agency's environmental health team will investigate.
