St Louis Encephalitis

St. Louis Encephalitis is an important mosquito-borne disease in the USA. This virus like other arboviruses, is maintained in nature through biological transmission of virus between vertebrate hosts and blood-sucking arthropods. During an SLE epidemic, large numbers of people become infected, however, only a very small percentage of the SLE infections are systematic and the majority are never diagnosed.

Symptoms range from mild headaches, coma or in rare cases death. Other symptoms include fever, nausea, stiff neck/back, light sensitivity, confusion, drowsiness, irritability, and motor skill impairment. Wild bird populations are central to the transmission cycle. An infected bird can produce an appreciable amount of virus in one or two days, but the virus disappears two to three days later, so a bird remains "infective" for only a few days. Birds do not show any symptoms of disease and become immune after exposure.

Culex nigripalpus mosquitoes in Florida are the major vector. There is no cure for the disease nor are there vaccines available. Medical treatment is available only for the symptoms. Control of the disease relies upon preventing transmission to humans or breaking the virus cycle in nature, such as reducing vector mosquito population.