For 30 years until last summer, children and adults were dropping dead from cardiac arrest, often mid-conversation, in the remote mountain villages of China’s Yunnan province that fringes northeast India.
This summer, after a five-year investigation spread from the Yunnan highlands to Beijing laboratories, one of China’s greatest medical mysteries stands nearly solved.
“The villagers were dying suddenly...many had no symptoms before they suddenly fainted and died. It became a very serious political concern,’’ recalled Robert Fontaine, an epidemiologist with the US Centres for Disease Control and Prevention, who worked with the Chinese to investigate the deaths in land so remote that the villagers don’t speak standard Chinese.
“In some villages, we could almost predict the week when the deaths would start,’’ said Fontaine at a media talk this week in Beijing to share the findings of his investigation. The sudden deaths sprung during the monsoon and peaked every July and August. The highest deaths were reported among 8-40 year-olds and women.
Sketching the last hours of the dead was not easy because many deaths were not witnessed, but a pattern slowly emerged. Most of the suddenly dead villagers had drunk surface water, eaten mushrooms, climbed a hill or suffered emotional stress. Most suffered chest pain and palpitations while dying. Autopsies found several had a heart lesion.
The investigators were reluctant to blame mushrooms. Yunnan is famed for supplying the world with mushrooms and locals are armed with the traditional knowledge of picking non-toxic varieties.
But laboratory tests on mushrooms and mice helped nab the elusive serial killer behind over 400 deaths since 1978 in Yunnan villages thousands of kilometres apart. The killer was a nearly unknown little white mushroom called trogia that lives on rotting wood and has no market value.
For decades during every rainy summer, the rural Yunnanese had picked and sold mushrooms and saved the worthless trogia for their own meals. Mushrooms concentrate heavy metals from the soil. Trogia was found to soak up high levels of barium, which can affect the heart muscles, nerves and emotions especially in people with an underlying heart condition. But the sudden deaths also struck people with healthy hearts.
Fontaine says that finals experiments are still continuing to isolate its toxins. But the problem has ‘virtually disappeared’ this summer, after Yunnan villagers were warned the killer was from their own forest kitchens.