What causes La Crosse encephalitis?
La Crosse encephalitis virus (LACV), an orthobunyavirus, is the cause of La Crosse encephalitis.
How do people get become infected with LACV?
People get La Crosse encephalitis from the bite of an infected mosquito, most commonly Aedes triseriatus, the treehole mosquito. The normal infection cycle is between the mosquito and small mammals such as squirrels, mice, and chipmunks. People are considered "dead-end hosts". That is, humans are rarely, if ever, have a high enough concentration of virus to pass the virus back to a mosquito.
Where in the US do LACV infections occur?
LACV encephalitis was first identified in La Crosse, Wisconsin, in 1963. LACV encephalitis (neuroinvasive, i.e, the severe form of the disease) has since been reported in 31 states plus Washington, D.C., from 1964 to 2010.
Neuroinvasive disease from La Crosse virus and related bunyaviruses, 1964-2010. Most of these cases were caused by La Crosse virus. A few cases were caused by much rarer bunyaviruses (e.g., Cache Valley virus). Cases are reported by state of residence. (CDC)
What are the symptoms of La Crosse encephalitis?
The symptoms are similar to those of infections with West Nile virus (WNV) and St. Louis encephalitis virus (SLEV).
- Many infected people show no symptoms
- Milder symptoms include fever, headache, nausea, vomiting, body aches
- Severe symptoms involve development of encephalitis (inflammation of the brain): severe headache, paralysis, coma
What is the recovery rate for LACV infections?
Full recovery is common; long-term chronic disability or death rarely occurs (mortality rate is less than 1%).
How is the disease treated? Is there a vaccine?
There is no vaccine for LACV encephalitis, and no specific treatment. Treatment is made on a case-by-case basis, depending on the severity of the symptoms.
Who is most at risk for infection with LACV?
While anyone in an area where LACV encephalitis occurs is at risk, children under the age of 16 are most likely to develop severe symptoms.
What is the best way to prevent infection with LACV?
The most effective ways to prevent infection with LACV is to minimize your exposure to mosquito bites. See the mosquito safety page for more information.
Where can I get more information about La Crosse encephalitis?
The Centers for Disease Control and Prevention is an excellent source of information. Scientific publications about La Crosse encephalitis can be obtained through PubMed.gov.