St. Louis Encephalitis

Infectious agent:  St. Louis Encephalitis Virus, member of the family Flaviviridae, genus Flavivirus.

Description of illness: Most persons infected with SLEV have no apparent illness. Initial symptoms of those who become ill include fever, headache, nausea, vomiting, and tiredness. Severe neuroinvasive disease (often involving encephalitis, an inflammation of the brain) occurs more commonly in older adults. In rare cases, long-term disability or death can result. There is no specific treatment for SLEV infection; care is based on symptoms.