Japanese encephalitis is a potentially severe infection of the brain transmitted by mosquitoes. It occurs occurs in large parts of Asia and the Pacific rim.

Japanese encephalitis (JE) is a viral infection of the brain transmitted to humans by mosquitoes in parts of Asia and the Pacific rim. The mosquitoes that transmit JE feed predominantly during the night, from dusk to dawn and are prolific in rural areas, where rice cultivation and pig farming are common. However, they have also been found in urban locations.

The risk for most travellers to Asia is very low, especially for short-term travellers visiting urban areas. The overall incidence of JE among persons from non-affected countries travelling to Asia is estimated to be less than one case per 1 million travellers. Risk varies on the basis of: destination, duration, season and activities. It increases for persons who intend to live or travel in risk areas for long periods of time and have rural trips during transmission seasons. Certain activities, even during short trips, where there is significant rural, outdoor or night time exposure e.g. fieldwork or camping can increase the traveller’s risk.

Most human infections with Japanese encephalitis virus do not result in symptoms. When symptoms do occur they include fever, headache and confusion. In symptomatic cases requiring hospitalisation mortality rates are high and neurological complications are common.

Prevention

The risk of acquiring JE can be reduced by insect bite avoidance, particularly between the hours of dusk and dawn, when Culex mosquitoes are most active.

Japanese encephalitis vaccine

A licensed JE vaccine; IXIARO® is available and is recommended to those intending to stay for long periods in rural regions where JE occurs during the main transmission season or whose planned activities increase their risk. The vaccination is recommended from the age of 2 months onwards.

Accelerated schedule

As of August 2015, the marketing authority for IXIARO® Japanese encephalitis vaccine has changed to include an accelerated schedule. Adults 18-65 years of age can be vaccinated as follows: first dose at day 0, second dose, 7 days after the first dose.