The curious case of mysterious deaths in Muzaffarpur left most of the epidemic researchers and doctors puzzled. The number of the deceased seemed to be growing at a fast pace with no valid rhyme or reason.

Over the past three years, when summer was at its peak in mid-May, there were many instances of children waking up with convulsions, high fever and loud cries. Not just kids, young and healthy individuals used to complain of sudden seizures and inexplicably slip into a coma. As strange as it sounds, the problem would automatically stop from July onwards, with the onset of monsoon.

Some attributed it to heat stroke, others credited it to pest infections and pesticide poisoning. But, no one could solve the bizarre outbreak in India. Leaving no fixed pattern, it would strike any random child without showing any visible trace of symptom in his siblings or playmates.

Struggling to search for an explanation, Dr Rajesh Yadav, an investigator with the India Epidemic Intelligence Service, moved to the city of Muzaffarpur and closely observed the cycle of events for three long years. The reason has finally been unearthed, and it’s shocking.

On Tuesday, a joint investigation published by India’s National Center for Disease Control and the India office of the Centers for Disease Control and Prevention in Atlanta published a report identifying the cause of this phenomenon. Turns out, the otherwise harmless fruit, lychee, when consumed on an empty stomach by malnourished children leads to death.

In 2015, when health officials instructed parents to feed a healthy evening meal to their children instead of the fruit, the number of deaths subsequently dropped down to almost 50 per cent.

Here’s how they decoded the mystery deaths

Lack of white blood cells: The subjects used to suffer from an acute brain swelling also known as encephalopathy. Over many years of research, clinicians realised that many sick children did not have fever. An analysis of their spinal fluid showed that they didn’t have an elevated count of white blood cells, implying that their body was fighting infection.

Low blood sugar levels: Some children had extremely low levels of glucose, which meant they were twice as likely to die.

Ackee fruit connection: A conference call with colleagues in Atlanta led the researchers to be aware of a “Jamaican vomiting sickness”, which had similar symptoms like convulsions, mental illness and brain swelling. There was a certain link to it as east Muzaffarpur produces almost 70 per cent of India’s lychee harvest, and the fruit – akin to ackee – also has high levels of hypoglycin, and a similar toxin known as methylenecyclopropyl glycine, or MCPG. Children often used to eat the unripe lychees lying on the ground. Since everyone in the region ate lychees, no one previously connected the fruit with the illness or deaths.

Metabolic imbalance: A test to find out hypoglycin in urine revealed alarming levels in the affected kids.

The mystery was solved!

Based on these findings, families were asked to make sure the children had healthy meals and were made to reduce the consumption of lychees, specifically keeping away from unripe ones.

The takeaway for the rest of the world from this? Be wary before eating unripe lychees on an empty stomach!