Four Dead and Dozens Hospitalized in Record California Mushroom Poisoning Surge
California is experiencing the largest known mushroom poisoning outbreak in U.S. history, with four deaths and 43 hospitalizations linked to toxic mushrooms, according to experts.
California’s deadly mushroom poisoning outbreak has hospitalized 43 people and killed four in the largest U.S. outbreak ever.
The outbreak, which began in November, has continued far beyond the normal mushroom growing season, leaving public health officials and mycologists searching for answers about why cases remain widespread across the state.
Anne Pringle
Three additional poisoning cases were reported earlier this week involving a family that picked mushrooms in Napa County over the weekend. According to Dr. Christine Wu, Napa County’s public health officer, the family gathered the mushrooms on Saturday, became ill Sunday and was hospitalized at Stanford Medical Center.
State health data shows victims have ranged in age from 19 months to 84 years old. Several incidents have involved family clusters who likely consumed the same batch of foraged mushrooms. California’s poison control system reported that four patients have required liver transplants during the outbreak.
Cases have now been identified in more than 10 counties across the San Francisco Bay Area and California’s central coast. After poisonings sharply increased late last fall, state health officials warned residents against eating 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.”
Experts say the main source of the poisonings is the invasive death cap mushroom, also known as Amanita phalloides. Another toxic species, the western destroying angel, or Amanita ocreata, has also been tied to several cases.
In a typical year, the United States records around 50 Amanita mushroom poisoning cases nationwide. California alone has nearly reached that figure already, with five new cases reported this month.
“What’s unusual about that — the season for death caps would typically be December and January,” said Anne Pringle, a professor of mycology at the University of Wisconsin-Madison. “Why is this happening?”
The outbreak has also highlighted weaknesses in California’s public health reporting system. Under current state regulations, health providers are not required to report amatoxin poisonings directly to public health agencies.
Instead, officials rely heavily on the California Poison Control System to identify and track cases.
“Right now, how we’re learning about these cases is actually through the California Poison Control System,” Wu said. “They’re trying to track these and then report them up to CDPH.”
Wu said the California Department of Public Health is working to make amatoxin poisoning a reportable disease.
The three family members poisoned over the weekend were not residents of Napa County, but authorities believe they collected the mushrooms in a rural section of the county.
“These individuals were reported to me only because … they found the mushrooms in Napa County,” Wu said, adding that there was no requirement she be notified. “That’s information that I can act on to protect the other community members in Napa.”
Health officials noted that most poisoning victims since November have spoken Spanish, although some patients also spoke Mandarin, Ukrainian, Russian, Mam and Mixteco.
Public health experts believe some individuals may be using foraging knowledge developed outside the United States, where certain edible mushrooms resemble California’s poisonous varieties.
“We know that the death cap and the western destroying angel, when they’re growing, look a lot like some of the native mushrooms that are edible in their home countries,” Wu said.
To increase awareness, Napa County has purchased radio advertisements in English, Spanish and Mixteco warning residents about poisonous mushrooms. California’s health department has also distributed informational flyers in nine languages.
“I’m really surprised that we haven’t been able to reach the Spanish-speaking community better, and that’s on public health,” Wu said. “So, we’re going to work harder for that.”
Death cap mushrooms originated in Europe and are believed to have arrived in California during the 1930s through imported nursery trees. Destroying angels are native to California.
Death caps usually grow near oak trees and sometimes pines. The mushrooms typically feature white gills, pale yellow or green caps and a ring around the stalk.
The amatoxins produced by these mushrooms can severely damage the liver, kidneys and gastrointestinal tract. Symptoms, including nausea, vomiting, diarrhea and stomach pain, may take up to 24 hours to appear. Severe liver damage can develop within two to three days, and even a small amount can be fatal.
Mike McCurdy, president of the Mycological Society of San Francisco, said death cap mushrooms were widespread over the weekend.
“This is a significant flush. It’s not just a fluky kind of thing, and it’s ranging all the way from Monterrey to Napa,” McCurdy said. “Nobody can remember a spring flush like this.”
McCurdy said he found more than 20 visible mushroom growths around five coastal live oak trees after searching for about 20 minutes on Saturday.
Pringle said researchers still do not understand why death cap mushrooms are appearing in unusually large numbers and persisting so late into the season.
“It’s interesting and frightening,” she said.
She also emphasized that mushrooms remain understudied compared with plants and animals and receive significantly less scientific funding.
“Science needs funding to solve this problem,” she said. “If I could figure out a way to stop its invasion, that would enable me to stop the poisonings.”
