Saint Louis encephalitis

The St. Louis encephalitis is the most common disease caused by arboviruses in North America and is also of travel medical importance.

Pathogen

The St. Louis encephalitis is triggered by the St. Louis encephalitis virus. The enveloped, single-stranded RNA virus of positive polarity belonging to the genus Flavivirus of the Flaviviridae family.

Transmission

The virus is transmitted by mosquitoes ( genus Culex, Stegomyia albopicta ). During a blood meal on an infected animal, the mosquitoes take on the virus and can transmit it to humans or animals at a later time by re- engraving. Animal reservoir are birds and bats. Man is only an accidental host, a transfer from person to person does not occur.

Occurrence

Endemic areas in the U.S. are the Ohio - Mississippi Basin, Texas, Florida, Colorado and California, as well as Jamaica. The virus is endemic in Canada, Central and South America, but there has probably been no epidemics. The transfer takes place, according to the life cycle of mosquitoes, most often between July and October.

Clinic

The disease is in most cases inapparent and without consequences. In 1-5 % of those infected but it comes too suddenly after an incubation period of a few days the onset of high fever, accompanied by headache and body pain, photophobia, and dizziness. Particularly in elderly persons can neurological symptoms following: meningitis or encephalitis. The recovery can take weeks and months are also possible permanent neurological deficits, such as gait and speech disorders. The mortality can be as high as 20%.

Therapy

No specific treatment or vaccine does not exist. For travelers to endemic areas is therefore a protection against mosquito bites is recommended as prevention: repellents, mosquito nets, bright, long clothing, avoiding outdoor stays during and after dusk.