California health authorities have issued a public health warning regarding wild mushrooms following nearly two dozen poisonings, including one fatality, attributed to the highly toxic Amanita phalloides, commonly known as the death cap mushroom. The California Department of Public Health (CDPH) reported 21 confirmed cases of toxic mushroom poisoning between mid-November and last Friday, leading to severe liver damage in multiple individuals, some requiring intensive care and potential liver transplants.
Current Public Health Advisory
The CDPH confirmed 21 cases of toxic mushroom poisoning between mid-November and last Friday, with one adult fatality. Several individuals, including children, experienced severe liver damage, and at least one patient is a candidate for a liver transplant. Clusters of cases have been identified in the Monterey and San Francisco Bay Areas, prompting a statewide risk alert. Dr. Erica Pan, CDPH director, advised the public against foraging for wild mushrooms, as death cap mushrooms can be easily mistaken for edible varieties.
Characteristics and Distribution
Death cap mushrooms (Amanita phalloides) grow in many parts of California, with their proliferation stimulated by fall and winter rainfall. An increase in rainfall this season has created conditions favorable for the mushrooms, similar to December 2016, when 14 cases of death cap poisoning were reported in the state. That incident resulted in three individuals requiring liver transplants and one child sustaining permanent neurological impairment.
Globally, death cap mushrooms are responsible for approximately 90% of mushroom-related fatalities. Historical accounts attribute the deaths of Roman Emperor Claudius (54 AD) and Holy Roman Emperor Charles VI (1740) to this species. Sightings and poisonings have also occurred in other U.S. regions, including the Midwest, Northeast, and Mountain West, with reports in Boise, Idaho, in October.
Originating in Eurasia, Amanita phalloides is now present in North America and Australia. Its presence in Central California is believed to date back to the 1930s, introduced inadvertently via the roots of imported European oak trees. Mycologist Anne Pringle of the University of Wisconsin-Madison has identified Northern California as a significant area for death cap growth. These mushrooms typically grow near oak, pine, and other hardwood trees, often in dispersed groups within urban and suburban wooded areas.
Death cap mushrooms can resemble edible varieties, particularly in their immature "button" stage. They typically reach a medium-to-large size, up to 6 inches across and 6 inches tall, with a greenish-gray cap that progresses from dome-shaped to flattened. Distinctive features include white gills, a white ring on the stem, and a large white sac at the base. According to mycologist Britt Bunyard, the mushroom's taste and smell can be described as "quite nice," offering no indication of its toxicity.
Toxicity and Symptoms
Ingestion of half a death cap mushroom or less can be lethal, with mortality rates post-ingestion potentially reaching 50%. Estimates suggest death cap mushrooms cause approximately 10,000 illnesses and 100 deaths worldwide annually.
The mushroom produces α-Amanitin (AMA), a highly toxic peptide that is resistant to various environmental factors, including heat, cold, drying, freezing, and stomach acid. According to the Food and Drug Administration (FDA), AMA poisoning symptoms typically begin 6 to 15 hours after ingestion, though sometimes up to 48 hours.
Initial symptoms include sudden stomach pain, persistent vomiting, watery diarrhea, and extreme thirst, which may subside after about a day. A period of apparent recovery may follow, but this generally precedes a rapid decline in health, marked by severe weakness, prostration, and pain. The toxin causes irreversible damage to the liver, kidneys, cardiac tissue, and skeletal muscles, often leading to coma and death within four to eight days. Recovery, if it occurs, may take at least a month and is associated with liver enlargement.
Treatment and Prevention
Effective treatments for death cap poisoning are limited. Medical interventions often include administering activated charcoal, high doses of penicillin, and the drug silibinin, alongside rehydration and, in some severe cases, liver transplants.
Recent research conducted in 2023 by Chinese and Australian scientists explored potential antidotes. They identified the FDA-approved medical dye Indocyanine Green (ICG) as effective in treating AMA poisoning in mice. However, its efficacy in humans requires further clinical trials.
California health officials advise the public to consume only mushrooms obtained from reputable commercial sources. In the event of suspected mushroom poisoning or the onset of symptoms after consuming foraged mushrooms, immediate medical attention at a hospital is recommended.