The Kalachi Sleeping Sickness
Later explainedSummary
In a village in northern Kazakhstan, people began falling asleep. Not tired: asleep, suddenly, sometimes mid-conversation, and then unrousable for days. They woke with memory loss, weakness, nausea, and in some cases hallucinations. Children saw things that were not there.
The village sits on top of abandoned Soviet uranium mines, and so everybody, including a great many journalists, knew immediately what the answer was going to be.
It was not radiation. It was carbon monoxide.
The mines mattered. They just did not matter for the reason everyone assumed.
What is documented
The onset. From the spring of 2013, residents of Kalachi began experiencing sudden episodes of prolonged sleep. People fell asleep abruptly, in some cases while walking or talking, and remained asleep for periods measured in days.
The symptoms. On waking: memory loss, disorientation, weakness, nausea, headache, dizziness. Some, including children, reported hallucinations.
The scale. The episodes came in waves over roughly two years and affected on the order of a hundred to two hundred people, in a village of a few hundred.
What was tested, and excluded. Infection. Radiation. Water contamination. Food. The affected were examined and the village was surveyed. Kazakh authorities and outside investigators looked, repeatedly, for a pathogen or a radiological source, and did not find one.
The mines. Kalachi lies beside the former Soviet uranium mining settlement of Krasnogorsk. The mines beneath the area were abandoned after the collapse of the Soviet Union, and they flooded.
The finding. In 2015 the Kazakh government announced the cause. The mines were emitting carbon monoxide, together with elevated concentrations of hydrocarbons. The gas was accumulating in homes. Measurements found carbon monoxide at levels well above normal, and correspondingly depressed oxygen.
The response. The government relocated the greater part of the village.
Leading explanations
Carbon monoxide poisoning from the flooded mines. Established.
Carbon monoxide binds to haemoglobin far more readily than oxygen does, and displaces it. The result is that the blood carries less oxygen, and the organ most sensitive to that is the brain.
The clinical picture of carbon monoxide exposure is not obscure. It produces headache, dizziness, confusion, nausea, memory impairment, loss of consciousness, and, at sufficient exposure, hallucinations. Prolonged unconsciousness is exactly what it does.
The gas is colourless and odourless. Nobody in Kalachi could have detected it, and it was accumulating in their houses while they slept.
Why the mines matter, and why the assumption about them was wrong. Everyone reached immediately for uranium, because the mines were uranium mines and radiation is what uranium mines suggest. The measurements did not support it.
What the flooded workings were doing was displacing and venting gas: carbon monoxide and hydrocarbons, forced up through the ground and into the village above.
The mines were the cause. They were not the cause anybody guessed.
What the popular version gets wrong
"It was radiation from the uranium mines." It was not. Radiological surveys did not find levels that could account for it, and radiation does not produce that clinical picture. The uranium was a coincidence of geography, and it very nearly derailed the investigation, because it was such a satisfying answer.
"Nobody ever explained it." The Kazakh government announced the cause in 2015 and relocated the village. It is one of the fastest resolutions of a mass health episode in this archive.
"It was mass hysteria." It was not, and the registry files it under Mass and Collective while stating that plainly. This is a case in a category full of psychogenic episodes, and it is the counter-example. There was a real, physical, measurable poison, and the people of Kalachi were being poisoned by it.
The lesson runs in the direction opposite to most of this category. When a village reports something impossible, it is usually psychogenic. Sometimes it is a gas, and the only way to know which is to go and measure the air.
Current status
Later explained. Cause identified, announced, and acted on. The village was largely relocated.
The registry keeps this record beside the Dancing Plague and Tanganyika precisely because it is unlike them. It looks exactly like a mass psychogenic episode: a strange, dramatic, contagious-seeming affliction, in a stressed and isolated community, with an obvious folk explanation ready to hand.
It was carbon monoxide, and the difference was established by putting a meter in somebody's living room.
Sources
- Government of Kazakhstan, announcement of the findings, 2015: elevated carbon monoxide and hydrocarbon concentrations attributed to the flooded mine workings.
- Environmental and medical investigations of Kalachi and the former Krasnogorsk mining area, 2013 to 2015.
- Clinical literature on carbon monoxide poisoning and its neurological effects.
- Contemporary reporting on the village and on its relocation.
Last reviewed: July 2026. Records are provisional. Where the evidence changes, the entry changes. Found an error? Tell us.