Acute Encephalitis Syndrome (AES)

Acute Encephalitis Syndrome (AES)


Muzaffarpur district in Bihar including Sheohar, Vaishali and East Champaran districts are reeling under the outbreak of Acute Encephalitis Syndrome (AES) or Japanese Encephalitis. AES has so far affected over 600 children and claimed more than 140 lives. The deaths of most of the children have been attributed to low blood sugar level (hypoglycaemia).

What is AES?

AES, also known as ‘Chamki Fever’ or Litchi Virus in India, is an umbrella term used for infections that causes inflammation irritation or swelling on the brain.


Apart from sources like as fungus, bacteria, chemical, parasites, toxins and spirochetes to reported to be the cause of AES over the past few decades, viruses have also been attributed mainly to be the cause of AES in India.  In addition to viral encephalitis, severe form of toxoplasmosis and leptospirosis can cause AES. Apart from this, the causative agent of AES varies with geographical location and season

What is the link between AES and Litchi Fruit?

The logic behind the link between Litchi fruit consumption and AES is that when children eat large amounts of unripe litchi fruits (on an empty stomach), it may lead to hypoglycemic encephalopathy, a brain injury that causes prolonged or severe hypoglycemia or low blood sugar. Unripe litchi has the toxins hypoglycin A and methylene cyclopropyl glycine (MCPG) that causes vomiting if ingested in large quantities. An India-U.S. team confirmed the role of the toxin MCPG in 2017.

Well-nourished children are not affected by the consumption of Litchi fruit. AES affects only undernourished children who consumed litchi fruit the previous day and went to bed on an empty stomach.

However, while linking litchi fruit to AES deaths (owing to the presence of infectious organism) is well documented, this alone cannot be attributed as the main cause of death. Some recent findings by specialists have narrowed down reasons for AES to multiple other factors like humidity, malnutrition, heat and poor hygiene.


AES complications may include memory loss, coma and even death. The signs and symptoms typically include:

  • High Fever
  • Headache
  • Vomiting
  • Confusion
  • Seizures
  • Sensitivity to light
  • Stiff neck and back
  • Memory loss
  • Problems with speech or hearing
  • Drowsiness
  • In some severe cases, paralysis and coma

Who is affected?

  • It mostly affects people below 15 years.
  • Acute Encephalitis Syndrome (AES) has its endemic zones covering the Gangetic plain like states of Bihar, Assam, east UP, West Bengal and some parts of Tamil Nadu.


We can treat Acute Encephalitis Syndrome (AES) using antibiotics, antiviral medication and supportive care. The treatment for hypoglycaemia includes supplying dextrose, a simple sugar similar to glucose, intravenously. Other measures include:

  • Ensuring children eat cooked meals before going to bed
  • Keeping children, under parental supervision, from eating unripe and too many litchis


AES can be prevented by:

  • Proper sanitation facilities
  • Increasing access to safe drinking water
  • Improve nutritional status of children at risk of AES
  • Preventive measures should be directed at reducing the mosquito density. Personal protection against mosquito bites by using mosquito nets treated with insecticide is recommended. Other methods like wearing fully covered, loose fitting clothes, use of repellents, etc have to be adopted to avoid mosquito bites
  • The transmission risk increases when animal sheds (especially piggeries) and human dwellings are situated very close to each other.
  • Vaccination: As per the guidelines of Government of India, two doses of JE/AES vaccine have been approved to be given one together with measles at 9 months of age and the second with DPT booster at 16-24 months of age.

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