Incubation period: approximately 2 weeks
Many cases are subclinical.
Clinical features of symptomatic cases:
(1) fever >= 39°C, often high
(2) headache
(3) lethargy
(4) nausea and vomiting
(5) abdominal pain and/or diarrhea
(6) pains in different parts of the body
(7) signs of meningeal irritation with nuchal rigidity
(8) depressed consciousness, which can progress to coma
(9) acute behavioral changes
(10) variable paralysis
(11) seizures
(12) cranial nerve palsies
(13) abnormal reflexes
(14) extrapyramidal signs (masked facies, rigidity, choreoathetosis)
(15) disordered movements and/or ataxia
Laboratory findings:
(1) peripheral leukocytosis
(2) hyponatremia
(3) CSF shows lymphocytic pleocytosis with no or mild elevation of protein
(4) cultures of CSF and blood negative for bacteria and fungi
MRI studies show high signal intensities in the thalami, hippocampi, brainstem and cerebral cortex.
Outcome:
(1) Mortality is relatively high and can reach 40% in the elderly. Death may be due to respiratory failure, uncal herniation or other cause.
(2) Approximately a third of patients recover completely.
(3) The remainder show some degree of neurologic deficit.
