Yunnan Sudden Death Syndrome Linked to Little White Mushrooms

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Every year, during the height of the rainy season, villagers of all ages in the rural highlands of Yunnan, in southwestern China, would die suddenly of cardiac arrest. They called it the Yunnan Sudden Death Syndrome, and no one knew what caused it. After a five-year study, China’s Center for Disease Control and Prevention believes it has found the cause: a mushroom known as Little White.

In the past three decades, an estimated 400 deaths have been blamed on Yunnan Sudden Death Syndrome. In the hours before death, about two-thirds of the victims had such symptoms as nausea, dizziness, heart palpitations, seizures, and fatigue. More than 90% of the deaths occurred in July or August, the midsummer rainy season.

"This very obvious clustering of deaths in villages [occurred] in very short periods of time in the summer," said Robert Fontaine, an epidemiologist who helped in the investigation. "It appears that there was something a little different going on."

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It wasn’t until 2004, when the China Field Epidemiology Training Program took over, a unit of medical investigators from the CDC, that investigators found three factors common to most victims – they drank surface water, had emotional distress, and ate wild mushrooms.

By the end of 2005, investigators began issuing warnings to villages to avoid eating unfamiliar mushrooms, but the Yunnan province is legendary for its wide variety of wild mushrooms, many of which are exported at high prices.

In 2008, investigators zeroed in on a previously unknown mushroom found in a number of homes where people died. The “Little White”, as it is called, is not sold in markets because it is too small and turns brown shortly after picking. The mushroom belongs to the Trogia genus and has three toxic amino acids, but known shown at high enough levels to cause death.

Many of the victims, though, showed high levels of barium, a heavy metal in the soil that seeps into mushrooms. Small amounts can trigger heart rhythm changes, breathing difficulties, increased blood pressure, swelling of the brain and liver, and kidney and heart damage.

“There is a lot of work left to do,” said Fontaine, who plans additional lab investigations to solve puzzle of the Yunnan Sudden Death Syndrome. Educational campaigns have appeared to work. The number of deaths has dramatically reduced, with none occurring so far this year.

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