Neurologic Infections in Travelers

Malveeka Sharma, MD, MPH; Joseph R. Zunt, MD, MPH


Semin Neurol. 2019;39(3):399-414. 

In This Article

Japanese Encephalitis


Japanese encephalitis (JE) is a flavivirus transmitted by the Culex mosquito, is the most common vaccine-preventable cause of encephalitis in Asia, and is endemic in 24 countries in South-East Asia and the Western Pacific. Case fatality is upwards of 30%, and those who survive often suffer permanent neuropsychological disability.[60] Approximately 50,000 cases of JE are diagnosed annually, with approximately 15,000 deaths.[2,60] Infection is common in children living in endemic regions, but travelers of all ages are at risk of developing infection.[61] Transmission occurs year-round in the tropics and subtropics.

Life Cycle, Ecology, and Species

The main animal hosts are aquatic birds and pigs. The Culex mosquito acquires the virus and is transmitted to human hosts through the mosquito bite.

Clinical Manifestations

Less than 1% of infected human hosts develop clinical disease. The incubation period lasts 5 to 15 days, with initial symptoms of fever, headache, and vomiting. The classic description of JE is parkinsonian features with masked facies, tremor, cogwheel rigidity, and choreoathetoid movements. Other neurologic manifestations include meningoencephalitis, acute flaccid paralysis, and cranial nerve palsies. Seizures are common among children.[2,61]


The clinical presentation and living in or recent travel to endemic regions should raise suspicion for JE. CSF analysis typically reveals a lymphocytic pleocytosis. Viral specific IgM ELISA on serum or CSF can confirm infection.[61] Plaque reduction neutralization tests can be performed to confirm infection and differentiate between other closely related flaviviruses (such as dengue and West Nile viruses).[61] Neuroimaging can show characteristic bilateral thalamic hemorrhages.[2]


As there is no specific treatment of JE, supportive care is the mainstay of management. Severe cases necessitate hospitalization, which can improve survival rates through fluid resuscitation, respiratory support, pain control, monitoring and management of seizures.[61] The inactivated Vero cell culture vaccine is most commonly used for travelers to endemic regions who will either be traveling for extended periods of time or will be traveling outside urban areas.[61] A live-attenuated vaccine, SA 14–14–2, is the most commonly used vaccine in endemic regions.[60] Otherwise, vector control and personal preventative measures are encouraged.