In Knox County, Tennessee, two children were recently hospitalized due to La Crosse virus, a rare mosquito-borne illness, marking the county’s first cases this year; they are now recovering at home. Concurrently, a 66-year-old man in Ohio was also diagnosed with the virus. La Crosse virus, transmitted by the Aedes triseriatus mosquito, often causes no symptoms, but can lead to fever, headache, nausea, vomiting, and, in rare cases, severe brain inflammation (encephalitis), particularly in children under 16.

The CDC reports 30–90 cases annually, likely underdiagnosed, with over 1,500 cases and 15 deaths recorded between 2003 and 2024, primarily in states like North Carolina, Ohio, Tennessee, and West Virginia. The virus is spread through mosquito bites in wooded areas during dawn and dusk, with symptoms appearing 5–15 days post-bite.

Preventive measures include using insect repellents (e.g., DEET, Picaridin), wearing protective clothing, and eliminating standing water to reduce mosquito breeding. No vaccine or specific treatment exists, and severe cases may require hospitalization, with up to 15% of cases facing major neurological complications.

Health officials urge seeking emergency care for symptoms like seizures or mental changes, especially in children.