California health officials are warning the public after four deaths and three liver transplants linked to the highly toxic death cap mushroom, which has spread widely following a wet winter. Since November 18, the California Department of Public Health (CDPH) has reported over 35 cases of poisoning, many resulting in severe liver damage and hospitalization. Patients affected range from 19 months to 67 years old.

The death cap mushroom, notorious for its deadly amatoxins, is responsible for 90% of fatal mushroom poisonings worldwide. It grows in forests and city parks, often near oak trees, and can easily be mistaken for edible mushrooms. Experts emphasize that even small amounts can be fatal, and that cooking, drying, or boiling the mushroom does not neutralize its toxins.

Dr. Craig Smollin, medical director of the San Francisco Division of the California Poison Control System, described this year’s outbreak as unusually severe, calling it a “super bloom” caused by warm fall temperatures and early rains. “Having almost 40 cases is very unusual,” he said.

Several victims were seasonal farmworkers who mistook the death cap for safe mushrooms they knew from Mexico. One family in Salinas, California, ate the mushrooms over multiple meals. The husband eventually required a liver transplant, while his wife spent five days hospitalized.

Symptoms of death cap poisoning typically appear within 24 hours, including nausea, vomiting, stomach cramps, and diarrhea. While initial symptoms may temporarily improve, serious liver damage can develop within 2–3 days, sometimes requiring intensive care or a transplant.

Authorities have reported clusters of death caps across Northern California and the Central Coast, including Monterey and the San Francisco Bay areas. Public health warnings have been expanded in multiple languages, including Spanish, Mixteco, and Mandarin, as over 60% of poisonings affected Spanish-speaking individuals.

“Unless you are an expert in mushrooms, it is very difficult to identify safe varieties,” Dr. Smollin said. Children and pets are particularly vulnerable, and officials advise that mushrooms should only be purchased from trusted stores.

Health experts stress that treatment is most effective when sought early, urging anyone who suspects ingestion of a toxic mushroom to seek immediate medical care. The U.S. Poison Control Centers report a 40% increase in all mushroom exposures from September through January compared to the previous year. They can be reached at 1-800-222-1222 or PoisonHelp.org.

California residents are advised to avoid foraging wild mushrooms entirely this year. Experts warn that even small mistakes can be fatal, and public awareness is critical to preventing further deaths and severe liver injuries.