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Japanese Encephalitis
General Information:
– caused by Japanese encephalitis virus (JEV), closely related to West Nile virus
– transmission is through infected mosquito
– most common cause of vaccine-preventable cause of encephalitis in Asia
– Incubation period is 5-15 days
– <1% develop clinical, disease, most asymptomatic
– Acute encephalitis most common presentation
– Sx: altered mental status, focal neuro deficits, movement disorder, seizure, fever, headache,
vomiting
– Classic presentation: Parkinsonian syndrome with mask-like facies, tremor, cogwheel rigidity, and
choreoathtoid movements
– case-fatality is 20-30%
Area of the world affected:
-- Primarily in Asia – China, Japan, Korea, India, Southeast Asia
Relevance to the US physician:
1. JE
-- Should be considered in patients concerned for neurological infection with recent travel to
endemic country
-- Lab: JEV-specific IgM in serum (after 7 days of sx onset) or CSF (after 4 days of sx onset)
-- Viral culture and other viral RNA amplifications tests are not sensitive
-- Treatment is supportive
-- In survivors, 30-50% have significant neurological/cognitive/psychological sequelae
2. Vaccine
-- One vaccine (Ixiaro) is available in the US
-- 2 doses, 28 days apart (96% develop immunity)
-- No information on duration of protection
-- Recommended for travelers ≥ 1 month in endemic areas during JEV season
Bottom Line:
Very rare but deadly disease with high mortality and post-infection sequelae. Think about it in travelers to Asia during summer/fall seasons who have not been immunized.
University of Maryland Section of Global Emergency Health
Author: Veronica Pei
References
http://wwwnc.cdc.gov/travel/yellowbook/2012/chapter-3-infectious-diseases-related-to-travel/japanese-encephalitis.htm#2473