In the outbreak of acute encephalitis syndrome (AES) in Bihar, which has witnessed close to 350 cases and 103 deaths, most of these deaths have been attributed to hypoglycaemia, or low blood sugar. Hypoglycaemia is a commonly seen sign among patients of AES, and the link has been the subject of research over the years.

What causes AES?
AES is a broad term involving several infections, and affects young children. The syndrome can be caused by viruses, bacteria or fungi. In India, the most common cause is the virus that causes Japanese encephalitis (JE). Health Ministry estimates attribute 5-35% of AES cases to the JE virus.

The syndrome is also caused by infections such as scrub typhus, dengue, mumps, measles, and even Nipah or Zika virus. In the latest outbreak in Muzaffarpur, the cause is yet to be clinically identified in most of the children.

How is hypoglycaemia linked to AES?
The combination of AES with hypoglycaemia is unique. Hypoglycaemia is not a symptom but a sign of AES. In Bihar, convulsions in children (which is AES) are found in combination with hypoglycaemia. This hypoglycaemia is caused by malnourishment and lack of proper diet. With 98% of AES patients in Bihar also suffering hypoglycaemia, doctors are attributing deaths to the latter. A 2014 study suggested that hypoglycaemia was the trigger that led to diagnosis of encephalitis.

What explains the connection?
In 2014, a research paper, Epidemiology of Acute Encephalitis Syndrome in India: Changing Paradigm and Implication for Control’ drew a parallel between cases in Bihar’s Muzaffarpur and in Vietnam’s Bac Giang province. In both places, there were litchi orchards in the neighbourhood. The possible association with some toxin in litchi or in environment needs to be documented. Methylene cyclopropyl glycine (MCPG) which has been known to be a content of litchi fruit has been shown to cause hypoglycaemia in experimental animals.

However, this remains a subject of debate. “If toxins from litchi were causing hypoglycaemia, then these cases should have remained consistent each year and affected children of all socio-economic strata. This year, all deaths have all been recorded in the lower income groups. Cause of AES is still being researched- hypoglycaemic AES may be caused by malnutrition, heat, lack of rain, and entero-virus.

What is the history of AES in this region?
The first AES case was recorded in 1995 in Muzaffarpur. Eastern UP too sees frequent outbreaks. There is no fixed pattern, but a year with high temperature and scanty rain usually witnesses high cases. There were 143 deaths in 2013 and 355 in 2014, which dropped to 11 in 2017 and 7 in 2018.

What makes this region so vulnerable?
Malnutrition is high in both states, and malnourished children are prone to infection. Ministry of Health and Family Welfare data show UP and Bihar together account for over 35% of child deaths in country. National Family Health Survey-4 data show that in 2015-16, 48% children aged less than five in Bihar were stunted — the highest in India.

A team from the Centers for Disease Control, Atlanta, and Christian Medical College, Vellore, has concluded that heat, humidity, unhygienic conditions and malnutrition, unique to these areas, together contribute to the rise in AES. Incidence is higher in litchi fields around which malnourished children live.

How is the government tackling AES?
The Bihar government introduced free vaccines at all primary health centres. The current coverage is 70%. The central and state governments have conducted awareness campaign since February asking people not to expose their children to sun, ensure a proper diet and increase fluid intake.