La Crosse Virus

La Crosse virus has an incubation period of 3 to 7 days.

The vector for La Crosse is the forest-dwelling mosquito A. triseriatus, which is found throughout northeastern and northern Midwest United States. Other carriers of the virus include rodents and foxes, which act as amplifying hosts. Human infections typically occur in the summer and early fall, when mosquito bites are most likely. The incidence of disease is around 20 to 30 per 100,000, with a higher proportion in people living or working in proximity with forests.

Aedes triseriatus mosquito, vector for La Crosse Virus
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Symptomatology and Outcome
La Crosse encephalitis begins with rapid onset febrile illness, with symptoms including meningitis, malaise, headache and nausea. Approximately 50% of patients suffer from seizures and 30% go into comas. Symptoms typically end within seven days, with few sequelae. The only significant sequelae are epilepsy in 10-15% of children and paresis in 2% of cases.

Prevention and Management
Because the vector for La Crosse is a widespread mosquito host, control is quite difficult. Measures were taken in the past to kill control mosquito populations with insecticides, but due to ecological reasons that is no longer feasible. Control occurs mainly at the individual level with the use of mesh netting and mosquito repellant.

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