Bihar's annual AES outbreaks continue to mystify

Sweltering heat, litchi toxins, malnutrition, and poor healthcare facilities blamed for the recurring child-killing epidemic.

Vanita Srivastava

doi:10.1038/nindia.2019.82 Published online 2 July 2019

A child diagnosed with AES in a Muzaffarpur hospital.
“My son would have turned five this month,” says Gudiya Devi, sitting in her mud-and-thatch home in Jagarnathpur Dokra, a suburban tehsil in the eastern Indian state of Bihar. On June 2, she played with him, fed him dinner and watched as Subodh went to sleep peacefully, with no signs of uneasiness. But when she got up at 5 a.m., his body was stiff. “He had slipped into a coma,” the mother of four recalls.

Three days later Subodh Kumar died of Acute Encephalitis Syndrome (AES) at the Sri Krishna Medical College and Hospital (SKMCH) in Muzaffarpur district, the epicentre of the annual AES outbreaks, about 60 kms from Bihar’s capital Patna.

Devi’s husband Raj Kishore Kumar says the doctors had done their best. “We kept waiting for our son to open his eyes but he did not.”

Kumar earns between Rs 100 to Rs 300 each day. His wife chips in with a small sum as an agricultural labourer. His family is among hundreds who grappled this year with the AES outbreak (locally called chamki fever). More than 150 children have died this year in Muzaffarpur and its adjoining districts since the beginning of June. The disease starts in children – mostly between one and ten — with high fever, headaches and disorientation or delirium. Many quickly go into coma.

The outbreaks have become an annual event in the summer months in some districts of Bihar, killing hundreds of children and sending the inadequate public health system into meltdown.

Devi’s neighbourhood has many tragic stories. Three kilometres away in Seori Gopinathpur, Lali Devi’s son Raja Babu also died of AES on June 10. “He was fine just a day before. He even asked me for some money to buy a treat,” she says. Just like Subodh, the boy slept early but woke up at around 4am. “I gave him some water. Suddenly his condition started deteriorating and he lost consciousness,” she says. Lali’s  husband Birendra Sahni also earns around Rs 300 a day.

Heat, humidity, malnutrition and litchis

One common thread linking the outbreaks is the hot and humid months of May and June, says senior paediatrician, Arun Shah, who was part of the team led by virologist, Jacob John, that carried out extensive research on the Bihar AES phenomenon in 20141. “Also, all the children inflicted (with AES) are from very poor families and are severely malnourished,” he says.

In their study, Shah, John and colleagues had also identified a fruit toxin in unripe litchis as responsible for triggering low sugar levels (hypoglycaemia) and subsequently AES among children already suffering from malnutrition1. “The toxin methylene-cyclo-propyl-glycine (MCPG) in unripe litchi is merely a trigger. The predisposing factor is malnutrition," Shah clarifies.

Unripe litchis have fruit toxins that may trigger hypoglyceamia in malnourished children.

© Pixabay

Shah recommends that parents be made aware of the litchi trigger. “They should not let their children go into the litchi orchards or let them sleep on an empty stomach.”

Another study in 2017 by researchers from India's National Centre for Disease Control and the Center for Disease Control, Atlanta corroborated the litchi toxin link2. The study linked these seasonal deaths of children to consumption of litchi fruits laden with two naturally occurring toxins hypoglycin A and MCPG2. The researchers recommended minimising litchi consumption, ensuring that the children get an evening meal and are immediately supplemented with glucose in case of suspected illness.

However, Gopal Shankar Sahni, the head of paediatrics in Muzzaffarpur’s nodal healthcare facility SKMCH, dismisses the litchi connection. “The cause of death is heat stroke,” he says. Sweltering days and nights, with temperatures hovering between 37 and 40 degrees Celsius and humidity of 60 to 70 per cent make the district susceptible to AES, he says. The region experienced such high heat and humidity between June 5 and 23. This was main reason behind so many cases in 2019, Sahni says.

Acknowledging that malnutrition plays a role in the seasonal outbreaks, Sahni says the hot and humid spells don’t just drastically decrease the children’s blood sugar levels but also play havoc on their sodium and potassium levels. The litchi toxins can increase SGPT (a liver toxin) levels, but in AES patients, the SGPT levels were found only to be marginally high. “Besides, infants as young as seven months have been inflicted. Where did they get litchis from?” he questions.

Sahni says there were 700 cases of AES in 2014 but from 2015 to 2018, the number of cases was between 35 and 50. “If litchi was a causative or a triggering factor, why was the number of cases so low in the last four years?” To support his theory, Sahni points to the weather data between 2015 and 2018, when the summer temperature soared higher than 37 degrees Celsius and humidity passed 60 percent for just two or three days.

The litchi toxins, he says, cause vomiting and abdominal pain. “In our patients, there were no such clinical symptoms. They all had a common connect — convulsions and then a quick migration into coma,” he says.

A paralysed healthcare system

Experts maintain that malnutrition, heat, humidity and litchi toxins are not the only contributors to the epidemic. A lack of healthcare facilities and poverty in the region have compounded the tragedy.

Until May this year, SKMCH had only 14 paediatric beds. During the outbreak, each bed was being shared by multiple children. The number of beds has now been increased to 66.

Muzaffarpur suffers from poor infrastructure and a severe scarcity of doctors or trained nurses.
In 2014, around 140 children died of AES and India’s health minister Harsh Vardhan announced that the hospital would get a ‘super speciality’ upgrade. Five years hence, SKMCH is still bursting at its seams with the promised new building still to be operational. During the outbreak this year, Harsh Vardhan said the building will be ready by December 2019. He also made a fresh promise of a 100-bed paediatric ICU in the district, a virology laboratory and a robust interdisciplinary research mechanism. Muzaffarpur has 16 primary health centres but they suffer from poor infrastructure and a severe scarcity of doctors or trained nurses.

Asadur Rahman, chief of UNICEF Bihar, cites the National Family Health Survey of 2015-16 which showed that almost 20 per cent of under-5 children in Bihar were acutely malnourished and seven per cent were severely wasted, or had severe acute malnourishment. These children are most vulnerable to infections, diseases and death. Bihar has one Nutrition Rehabilitation Centre (NRC) per district. That's grossly inadequate, Rahman says.

Meanwhile, Gudiya Devi and Lali Devi have been visited by journalists, politicians, primary healthcare workers and NGO officials, trying to understand AES better. Raj Kishore says one important first step to plug the annual mortality is to make the region’s people aware of the results of scientific studies. “We need to know what causes this strange disease and how we can prevent our children from falling victim.” Otherwise, he says, it will resurface next June and they will be just as helpless.


1. John, T. J. & Das, M. Acute encephalitis syndrome in children in Muzaffarpur: Hypothesis of toxic origin. Curr. Sci. 106, 1184–1185 (2014)

2. Shrivastava, A. et al. Association of acute toxic encephalopathy with litchi consumption in an outbreak in Muzaffarpur, India, 2014: a case-control study. Lancet Glob. Hlth. (2017) doi: 10.1016/S2214-109X(17)30035-9