Ross County Mosquito Tests Positive for La Crosse Virus
Chillicothe, OH – A mosquito from a pool collected from Colerain Township in Ross County has tested positive for La Crosse Virus. No human cases have been reported.
The mosquito that primarily transmits La Crosse virus is the Eastern Treehole mosquito (Aedes triseriatus), an aggressive daytime biting mosquito commonly found in wooded areas. While no human cases have been reported in Ross County to date in 2026, according to the Ohio Department of Health (ODH), Ohio has reported more human cases than any other state in the United States averaging about 20 cases per year.
For this reason, it is crucial to be cautious of mosquito bites all throughout the day due to some mosquito species being active during the day as well as hours near dusk. The Ross County Health District recommends the following actions to help protect the community from mosquito bites and reduce the mosquito population:
- Dump out standing water around the home weekly.
- Dress in long pants and long sleeves whenever possible.
- Defend by using insect repellent containing any one of the following CDC-recommended ingredients: Picaridin, DEET, oil of lemon eucalyptus (or PMD), or IR3535.
Mosquito larvicide tablets are available at the Ross County Health District on a first come first serve basis for use in standing water that cannot be dumped.
About La Crosse Virus
According to the Centers for Disease Control and Prevention (CDC), La Crosse is a disease caused by a virus spread infected mosquitoes. Most people infected by the virus do not have symptoms. Initial symptoms can include fever, headache, nausea, vomiting, and fatigue. Some people may develop severe disease, including encephalitis (inflammation of the brain). Severe disease occurs most often in children under 16 years old. While not all mosquitoes carry this virus, the type of mosquito that spreads this virus is found throughout Ross County.
More information:
La Crosse Virus Disease in Ohio Map | Ohio Department of Health