The LaCrosse encephalitis virus has a complex life cycle involving chipmunks and squirrels and a specific type of woodland mosquito (Aedes triseriatus). This mosquito breeds in tree holes and manmade containers, and it bites during the day.
People are not an important part of the life cycle of the LaCrosse encephalitis virus. In rare cases, however, people who live in or visit an area where the virus lives can be infected by the bite of an infected mosquito. After infection, the virus invades the central nervous system, including the spinal cord and brain.
LaCrosse encephalitis is usually a mild illness, with symptoms including:
People with severe cases, usually children, may experience:
- Lasting brain damage.
It takes anywhere from 5 to 15 days after the bite of an infected mosquito to develop symptoms of LaCrosse encephalitis.
Diagnosis is based on tests of blood or spinal fluid.
Anyone can get LaCrosse encephalitis, but some people are at increased risk, such as:
- People who live in or visit woodland habitats
- People who work outside or participate in outdoor recreational activities in areas where the disease is common.