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Acute Encephalitis Syndrome

This topic provides information about Causes, target group, Signs & symptoms of Acute Encephalitis Syndrome.


Acute Encephalitis Syndrome (AES) including Japanese Encephalitis (JE) is a group of clinically similar neurologic manifestation caused by several different viruses, bacteria, fungus, parasites, spirochetes, chemical/ toxins etc. The outbreak of JE usually coincides with the monsoon and post monsoon period when the density of mosquitoes increases while encephalitis due to other viruses specially entero-viruses occurs throughout the year as it is a water borne disease.

Who is affected?

  • It predominantly affects population below 15 years.
  • There is seasonal and geographical variation in the causative organism.
  • JEV has its endemic zones running along the Gangetic plain including states of UP (east), Bihar, West Bengal and Assam, and parts of Tamil Nadu.

The epidemiological analysis of the data collected for the States from 2008-2013 revealed the following:

  • Most vulnerable age group between 1-5 years followed by 5-10 years and 10-15 years in that order.
  • Least JE infections in infants (0-1 year).
  • All the endemic States except Assam start reporting JE cases from July onwards attaining a peak in September-October. In Assam the cases start appearing from February and attain a peak in the month of July.
  • Due to circulation of entero-viruses particularly in Eastern Uttar Pradesh AES cases are reported round the year.

In India, AES outbreaks in north and eastern India have been linked to children eating unripe litchi fruit on empty stomachs. Unripe fruit contain the toxins hypoglycin A and methylenecyclopropylglycine (MCPG), which cause vomiting if ingested in large quantities. Hypoglycin A is a naturally occurring amino acid found in the unripened litchi that causes severe vomiting (Jamaican vomiting sickness), while MCPG is a poisonous compound found in litchi seeds that causes a sudden drop in blood sugar, vomiting, altered mental states leading to lethargy, unconsciousness, coma and death. These toxins cause sudden high fever and seizures serious enough to require hospitalisation in young, severely malnourished children.

Signs and Symptoms

Acute encephalitis syndrome (AES) is characterized by an acute onset of fever and clinical neurological manifestation that includes mental confusion, disorientation, delirium, or coma. Apart from viral encephalitis, severe form of leptospirosis and toxoplasmosis can cause AES. Keeping in mind the wide range of causal agents and the rapid rate of neurological impairment due to pathogenesis, clinicians face the challenge of a small window period between diagnosis and treatment.


  • Increase access to safe drinking water and proper sanitation facilities
  • Improve nutritional status of children at risk of JE/AES
  • Vector control :
    • The preventive measures are directed at reducing the vector (mosquito) density.
    • JE vectors are exophillic and endophagic in nature. The risk of transmission increases when the human dwellings and animal sheds particularly piggeries are situated very close to each other. Piggeries may be kept away (4-5 kms) from human dwellings. When they are situated far from each other, the risk of transmission is reduced.
    • Personal protection against mosquito bites using insecticide treated mosquito nets. 
    • Clothing reduces the risk of mosquito biting if the cloth is sufficiently thick or loosely fitting. Long sleeves and trousers with stockings may protect the arms and legs, the preferred sites for mosquito bites. School children should adhere to these practices whenever possible.
    • Household insecticidal products, namely mosquito coils, pyrethrum space spray and aerosols have been used extensively for personal protection against mosquitoes. Electric vaporizer mats and liquid vaporizers are more recent additions which are marketed in practically all urban areas.
    • Repellents are a common means of personal protection against mosquitoes and other biting insects. These are broadly classified into two categories, natural repellents and chemical repellents. Essential oils from plant extracts are the main natural repellent ingredients, i.e. citronella oil, lemongrass oil and neem oil.
    • The reduction in mosquito breeding requires eco-management, as the role of insecticides is limited.
  • Vaccination : As per Govt. of India guidelines, 2 doses of JE vaccine have been approved to be included in UIP to be given one along with measles at the age of 9 months and the second with DPT booster at the age of 16-24 months w.e.f. April, 2013.

National Programme for Prevention and Control of Japanese Encephalitis/Acute Encephalitis Syndrome

Several government initiatives have been undertaken to educate and improve the hygiene of people living in the JE endemic zones. Government and non-government organizations have been instrumental in providing proper nutrition to the AES-affected population as most of the affected people belong to the lower economic strata of the society.

Govt. of India, as part of the National Programme for Prevention & Control of JE/AES, follows a multi pronged strategy encompassing preventive (sanitation, safe drinking water, improvement in nutrition etc.), case management (capacity building of medical and para-medical staff, referral etc.) and rehabilitation (physical and social rehabilitation of disabled children), measures to address the problems relating to JE/AES.

Sources :

  1. Guidelines for clinical management of AES including JE
  2. Operational Guidelines - National Programme for Prevention andControl of Japanese Encephalitis/Acute Encephalitis Syndrome

Related resources

  1. WHO Fact Sheet on JE
Kathi Jun 30, 2019 09:04 AM

However this disease is terrible

Shiny Jun 21, 2019 03:01 PM

Thanks for the information , yesterday I went with my baby for 9 month vaccination in thayi card govt mentioned MR 1, vitamin a and JE 1 injection but they gave only MR injection I asked nurse what about others two vaccination they told govt provided only MR injection others is not supplying so what we should do y govt is not providing facility so please provide the facilities of vaccination what they mentioned in the card

Augustine Sebastian Jun 20, 2019 08:19 PM

AES or acute encephalitis syndrome in Muzafarpur area are previously also known for outbreaks, co incidentally this out break co incided with litchi harvesting season and blaming the poor fruit is like hanging an innocent person, AES is caused by other factors also like polluted drinking water, lack of sanitation, JE caused by pig rearing (as pigs egrets and some wild animal & birds are hosts of the virus and is accidently transmitted to humans then it spreads rapidly), leptospirosis etc.
first of all improve the nutrition of antenatal mothers and children in the age group of 0-15 years, malnutrition is the main cause of meningal infections where the immune system is weak, Bihar, West Bengal and eastern Uttar pradesh have the lowest level of quality of life and living conditions, to prevent such incidences the Govt. of these states should focus on poverty alleviation, education, safe drinking water supply, sanitation & sustainable employment, better health services in rural areas, there is no lack of funds under National Health Mission but is pocketed by the corrupt at the expense of the poor and the ill informed general public,

Augustine Sebastian Jun 20, 2019 08:16 PM

it is manageable if one follows guidelines for prevention, management and control of AES by the NVBDCP.

brajesh Jun 19, 2019 01:45 AM

thanks for information

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