4 November 2011
Acute encephalitis in India
An increased number of cases of acute encephalitis syndrome (AES) with unknown aetiology have been reported in a number of states in India . Some of these cases have been confirmed as Japanese encephalitis (JE).
As of October 2011, there have been an estimated 6,160 cases of AES and JE with 844 deaths. The majority of cases have occurred in four states: Uttar Pradesh (3,021 with 462 deaths), Assam (1,319 cases with 250 deaths), West Bengal (589 cases with 40 deaths), and Tamil Nadu (502 cases and 14 deaths). Case numbers appear to be higher than over the previous five years .
In 2011, confirmed JE cases have been reported from the states of Kerala, Tamil Nadu, Karnataka, Assam, Manipur, Bihar, Jharkhand, West Bengal and Haryana . In September, cases of JE were reported from the city of Delhi for the first time [1, 3, 4].
JE is a flavivirus, transmitted to humans by Culex mosquitoes. JE is endemic throughout most countries of east and South East Asia. View a map of Japanese encephalitis risk areas. In India, the transmission season of JE occurs during and just after the monsoon season.
Advice for travellers
The risk of JE for travellers who stay for short periods in urban areas is very low. The risk is greater for persons who intend to live or travel in risk areas for long periods of time, and have rural trips during transmission seasons. All travellers to risk areas should be advised to practise insect bite avoidance measures, particularly between dusk and dawn, when Culex mosquitoes are most active.
JE vaccine should be considered for long-term travellers and expatriates and those intending to visit or work in rural agricultural areas such as rice fields and marshland.
Further information on JE and other health risks in India can be found on the NaTHNaC Country Information Page.
1. India National Vector Borne Disease Control Programme. Japanese encephalitis: AES/JE cases in the country since 2007. October 2011. [Accessed 4 November 2011]. Available at: http://www.nvbdcp.gov.in/je-cd.html
2. India National Vector Borne Disease Control Programme. Disease Outbreak/Alert Reported in 2011 - IDSP. Week 1 to Week 40. [Accessed 4 November 2011]. Available at: http://www.idsp.nic.in/idsp/IDSP/resource_idsp.jsp
3. Pro-Med. Japanese encephalitis and other – India. 2 November 2011. [Accessed 4 November 2011]. Available at:
4. Indian Council of Medical Research (ICMR), Japanese encephalitis. [Accessed 4 November 2011]. Available at: