Experts claim they have solved a long-running mystery as to why residents of a village kept falling into deep sleeps.
Locals in the Kazakhstan village of Kalachi dozed off for several days at a time, and there were other alarming side effects.
Some men awoke with a dramatic increase in sexual desire.
"The doctors laugh, and the nurses blush, when they see our men in this state," said one villager whose husband was a "victim" of this condition.
Residents were prone to violent hallucinations, with children especially badly hit.
One girl imagined she saw an elephant's trunk on her mother, while a terrified boy was convinced horses and light bulbs were flying around him.
New research links the weird condition to secret chemicals – likely used by the Red Army – stashed in underground containers close to the village.
These leaked into the water system causing the extreme drowsiness and other symptoms suffered by locals, said epidemiologist Professor Byron Crape, who led the study.
The strange “sleeping sickness” at Kalachi was so bad that the village was officially closed five years ago and most residents moved out – although some refused to do so.
Theories surrounding ‘sleeping sickness’
Thousands of tests were carried out but the origin of the condition remained unidentified, except a suspicion that it was linked to a disused Soviet-era uranium mine at nearby Krasnogorsk.
Four years ago the Kazakh government and international scientists linked the “sleeping sickness” to “high carbon monoxide and hydrocarbon concentrations” poisoning villagers from the mothballed mine.
Others claimed it was radiation, while one local had convinced his neighbours that an extraterrestrial force caused the condition by shining a beam through the village.
But now these theories have been debunked by new research in the “sleepy hollow” village by Dr Crape and experts from Nazarbayev University in Kazakhstan.
They rejected bacterial meningitis, genetic diseases and carbon monoxide as well as other more outlandish theories for the sleepiness.
Dr Crape said that having spoken at length to more than 200 present and former villagers, they realised that everyone bought their water from a single supplier who pumped it from an underground supply.
He believes military grade chemicals were buried underground at the disused mine and that these leaked into the water supply.
“The chemical seeps into the water, and if it is underground water, it eventually reaches the people in the village,” he said.
“Why do some fall asleep more often and several times, while others less often?
“Maybe some just get a higher concentration of the chemical, while others get less.”
Condition hit villagers for three years
Some 124 families who remained in the “sleeping village” no longer suffer from the condition which lasted from 2012 to 2015.
His hypothesis is that “the chemicals in barrels completely leaked into the water, and emptied” so there is no fresh pollution.
Cattle were not hit by droopiness – but their water came from a different supply, direct from a river.
"There was one single time when a woman complained that her cat slept abnormally long,” Dr Crape said.
“Guess what? It was a domestic cat that drank water from the same pump."
The mysterious symptoms came only in winter, but the professor believes this was because the unnamed chemical decomposed when the water was warmed more than 1C.
Further research will use a drone inside the “dangerous” mineshaft to continue the study.
He has not yet named the chemical suspected of causing the poisoning.
“I’m an epidemiologist, I don’t work in a chemical plant, I don’t work in military factories, but I’m trying to save lives,” he said.
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