California’s monthslong spate of mushroom poisonings, in which four people have died and 43 others hospitalized, has become the largest known outbreak of its kind in U.S. history, experts say.Three cases were reported earlier this week, long after the typical growing season for the mushrooms behind the illnesses, leaving public health officials and mycologists puzzled about why the poisonings have been so widespread and what is causing the trend.The three newest cases were among a family that had picked mushrooms in Napa County on Saturday, became sick Sunday and was hospitalized at Stanford Medical Center, according to Dr. Christine Wu, Napa County’s public health officer.AdvertisementAdvertisementSince the outbreak began in November, affected patients have ranged in age from as young as 19 months to as old as 84, according to the California Department of Public Health. Cases have come in clusters, with at least six involving families who likely shared the same batch of foraged mushrooms. Four people have received liver transplants, according to the state’s poison control system.Poisoning cases have been reported in more than 10 counties in the San Francisco Bay Area and along California’s central coast. After cases began to spike in late fall, California health officials warned people not to eat any foraged mushrooms.“This is definitely a much larger-than-usual outbreak. It is lasting longer and going much further into the year than we’d have anticipated,” said Heather Hallen-Adams, the toxicology chair of the North American Mycological Association. “ I don’t think we can really put a finger on why.”The death cap mushroom originated in Europe and is invasive in the U.S. (Anne Pringle)(Anne Pringle)The primary culprit behind the poisonings is the invasive death cap mushroom, which is also called Amanita phalloides. A second mushroom, called the western destroying angel, or Amanita ocreata, is responsible for a few cases. In an average year, about 50 cases of Amanita mushroom poisoning are reported nationwide — a total California has nearly hit on its own already. Five new cases have been reported this month.AdvertisementAdvertisement“What’s unusual about that — the season for death caps would typically be December and January,” said Anne Pringle, a professor of mycology at …
