One person has died in California following an outbreak of amatoxin poisoning linked to wild, foraged mushrooms, state health officials said.

The California Department of Public Health said more than 20 cases have been identified since mid-November, with clusters in the Monterey and San Francisco Bay areas. Several patients, including children, have suffered severe liver damage, and at least one person may require a liver transplant.

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The agency urged the public to avoid foraging entirely during what it called a high-risk season for toxic mushrooms. Officials said death cap mushrooms, among the most dangerous types, can be easily mistaken for safe, edible varieties and cannot be made safe by cooking.

“Death cap mushrooms contain potentially deadly toxins that can lead to liver failure," said Dr. Erica Pan, the state’s public health officer. “Because the death cap can easily be mistaken for edible safe mushrooms, we advise the public not to forage for wild mushrooms at all during this high-risk season.”

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Symptoms such as vomiting, diarrhea and abdominal pain typically appear within 6 to 24 hours but may briefly improve before severe or fatal liver damage can develop.

Death caps grow widely across the state, particularly near oak and other hardwood trees following fall and winter rains.