St. Louis Encephalitis Clinical Presentation

Updated: Jul 21, 2020
  • Author: Charurut Somboonwit, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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History and Physical Examination

After an incubation period of 4-21 days, St. Louis encephalitis virus (SLEV) infection can cause mild febrile illness, aseptic meningitis, or encephalitis. A prodrome of malaise and fever accompanied by cough and sore throat characterizes the onset of St. Louis encephalitis. Headache, nausea, vomiting, confusion, disorientation, irritability, tremors, and, occasionally, convulsions follow.

Several days after the onset of infection, the patient will defervesce, with gradual neurologic improvement over several days. Chronic infection does not occur, and relapsing infection has not been reported.

Most patients with SLEV infection develop a significant fever. Meningismus may or not be present. Photophobia is seldom present.

The neurologic examination findings are usually normal. Five percent of patients with SLEV infection present with deep coma, and 25% develop cranial nerve palsies. Fewer exhibit ataxia. Seizures are unusual and occur more frequently in children. [11]