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Japanese encephalitis in India (Assam)

25 July 2022

Indian media quoting the National Health Mission have reported 251 cases (including 38 deaths) of Japanese encephalitis in Assam in the first 3 weeks of July 2022. The disease has been reported in more than 20 of Assam’s 35 districts.

Japanese encephalitis virus (JEV) is a mosquito-borne virus which affects the central nervous system. It is most common around areas of rice and pig farming. JEV is transmitted from animals (mainly pigs/birds) to humans through the bite of an infected Culex mosquito which feeds in the hours around dusk. No human-to human transmission occurs.

Advice for Travellers

All travellers to endemic countries or outbreak areas are potentially at risk of infection. This risk is greatest for those:

  • travelling to rural areas during transmission seasons
  • participating in outdoor activities during twilight hours
  • travelling for a prolonged period of time

All travellers should be advised on:

  • the risks and potentially severe consequences of Japanese encephalitis
  • practicing strict mosquito bite avoidance measures, including correct use of insect repellents
  • minimising outdoor activities during twilight hours when Culex mosquitoes bite

Travellers at increased risk of developing severe clinical disease are those:

  • with pre-existing chronic medical conditions
  • younger than 10 years of age
  • older than 50 years of age

When to consider vaccination

For most travellers the risk of acquiring infection will be very small, but consider vaccinating those:

  • frequently exposed to bites in rural infected areas (e.g. backpackers, agricultural workers, volunteers)
  • at ongoing risk or repeatedly visiting 'high risk' areas (e.g. flood plains, rice paddies, marshlands, pig farms)
  • staying for short periods during epidemics/outbreaks
  • staying for long periods (e.g. more than one month) in infected areas
  • going to live in an endemic area

For further information, see the Japanese Encephalitis page.