PRESS RELEASE – The Williams County Health Department (WCHD) is reporting a confirmed human case of La Crosse Virus in a Williams County resident that was confirmed by the Ohio Department of Health. The case was in a pediatric patient residing in Edgerton, Ohio who was initially hospitalized and has recovered at home.
La Cross virus is a mosquito-borne illness primarily transmitted by the Eastern treehole mosquito, which is commonly found in wooded areas.
They prefer to lay eggs in pools of water found in tree holes, but will also lay eggs in man-made water-holding containers, especially discarded tires. Ohio reports more human cases of La Crosse virus than any other state, with 40 cases reported in 2025.
WCHD staff collected and tested mosquito samples from the area surrounding the reported case. At this time, no mosquito samples have tested positive for La Crosse virus.
Symptoms of La Crosse Virus
Many people infected with the La Crosse Virus have no noticeable symptoms. For those who do, symptoms typically begin five to 15 days after a mosquito bite and may include:
•Fever
•Headache
•Nausea
•Vomiting
•Lethargy
Severe disease most often occurs in children younger than 16. Symptoms may include:
•Seizures
•Coma
•Paralysis
•Neurologic complications after recovery
Death from an infection of La Crosse is rare and occurs in less than 1% of cases. There are no vaccines to prevent La Crosse and no medicines to treat it. You can reduce your risk of infection by preventing mosquito bites.
Prevention Tips
WCHD urges residents to follow these guidelines from the Ohio Department of Health to take an active part in reducing mosquito populations:
•Use insect repellent when you go outdoors. Mosquitoes may bite through clothing, so spraying clothes with repellent will provide extra protection.
•Repair or install screens on windows and doors to keep mosquitoes outside.
•Eliminate standing water from containers such as flowerpots, gutters, buckets, pool covers, pet dishes, tires, and birdbaths.
•Fill tree holes with dirt or sand to prevent mosquito breeding.
“While La Crosse virus cases are rare, they serve as an important reminder of how vital prevention and awareness are in protecting our community’s health.
“We work closely with our local and state partners to monitor mosquito activity and identify potential risks”, said Nathan Hoffer, Director of Nursing at the Williams County Health Department.
“The best ways to reduce this risk are to use mosquito repellent, wear long sleeves when outdoors, and remove standing water around your home to prevent mosquitoes from breeding.”
The Williams County Health Department will continue to monitor the situation and conduct mosquito surveillance and control efforts as needed.
For more information on mosquito-borne diseases and prevention, visit www.odh.ohio.gov/know-our-programs/zoonotic-disease-program/diseases/mosquito-borne-diseases.