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Acute Encephalitis Syndrome

  • Acute encephalitis syndrome is a severe case of encephalitis transmitted by mosquitoes and is characterized by high fever and inflammation of the brain.
Acute Encephalitis Syndrome by Legacy IAS Academy
  • The World Health Organisation (WHO) in 2006, coined the term AES to signify a group of diseases which seem similar to one another but are difficult to differentiate in the chaotic environment of an outbreak.
  • The disease most commonly affects children and young adults and can lead to considerable morbidity and mortality.
  • Causative Agents: Viruses are the main causative agents in AES cases, although other sources such as bacteria, fungi, parasites, spirochetes, chemicals, toxins, and noninfectious agents have also been reported over the past few decades. It is not vaccine-preventable.
  • Japanese encephalitis virus (JEV) is the major cause of AES in India (ranging from 5%-35%).
  • Herpes simplex virus, Nipah virus, Zika virus, Influenza A virus, West Nile virus, Chandipura virus, mumps, measles, dengue, scrub typhus, S.pneumoniae are also found as causative agents for AES.
  • Symptoms: include confusion, disorientation, coma, or inability to talk, high fever, vomiting, nausea, and unconsciousness.
  • Diagnosis: The National Vector Borne Disease Control Programme in India has set up countrywide surveillance for AES through sentinel sites with a focus on detecting Japanese encephalitis (JEV).
  • In the sentinel surveillance network, AES/JE is diagnosed by IgM Capture ELISA, and virus isolation is done in the National Reference Laboratory.

How is hypoglycaemia linked to AES?

  • Hypoglycaemia (low blood sugar) is a commonly seen sign among AES patients, and the link has been the subject of research for long.
  • The combination of AES with hypoglycaemia is unique to Muzaffarpur, Vietnam and Bangladesh.
  • A 2014 study in Muzaffarpur suggested that hypoglycaemia was the trigger that led to diagnosis of encephalitis.
  • So, Hypoglycaemia is not a symptom but a sign of AES.
  • With 98% of AES patients in Bihar also suffering hypoglycaemia, doctors are attributing deaths to the latter.

What is the litchi connect?

  • Early researches have drawn parallel between cases in Bihar’s Muzaffarpur and in Vietnam’s Bac Giang province.
  • In both places, there were litchi orchards in the neighbourhood.
  • Methylene cyclopropyl glycine (MCPG), also known as hypoglycin A, is known to be a content of litchi fruit.
  • Undernourished children who ate litchi during the day and went to bed on an empty stomach presented with serious illness early the next morning.
  • When litchi harvesting starts in May, several workers spend time in the fields.
  • There, it is common for children to feed on fallen litchis and sleep without food.
  • The toxin in litchi (MPCG) lowers blood sugar level during night, and these children are found unconscious in the morning.
  • Blood glucose falls sharply causing severe brain malfunction (encephalopathy), leading to seizures and coma, and death in many cases.

What role does malnutrition play?

  • If toxins from litchi were causing hypoglycaemia, then these cases should have remained consistent each year.
  • Also, it should have affected children of all socio-economic strata.
  • But in contrast, this year, all deaths have been recorded in the lower income groups.
  • While well-nourished children eating litchi remain unaffected even if they go to bed on an empty stomach, the under-nourished ones were at grave risk.
  • This is because under-nourished children lack sufficient glucose reserve in the form of glycogen.
  • Also, the production of glucose from non-carbohydrate source is unsafe as it is unsustainable and thus stopped midway.
  • This leads to low blood sugar level, giving way for further health complications.
  • In all, even if litchi is a triggering factor, the real cause for adverse effects is said to be malnutrition.


  • Dextrose is the name of a simple sugar that is made from corn and is chemically identical to glucose, or blood sugar.
  • Dextrose is often used in baking products as a sweetener, and can be commonly found in items such as processed foods and corn syrup.
  • For medical purposes, it is dissolved in solutions that are given intravenously, which can be combined with other drugs, or used to increase a person’s blood sugar.
  • As dextrose is a “simple” sugar, the body can quickly use it for energy.
  • Simple sugars can raise blood sugar levels very quickly, and they often lack nutritional value.
November 2023