California is facing the largest known outbreak of deadly mushroom poisonings in U.S. history, according to NBC News, with toxic wild mushrooms sickening dozens of people.

The California Department of Public Health issued a warning to health care providers Thursday, updating an earlier health advisory from January. 

Death cap and western destroying angel mushrooms have reportedly been collected in a wide variety of locations across California. These poisonous mushrooms can easily be mistaken for several edible mushroom varieties, even for experienced mushroom foragers.

Both death cap and western destroying angel mushrooms contain amatoxins, potentially lethal toxins that cannot be removed by boiling, cooking, or drying the mushrooms before consumption.

Since November, California Poison Control has recorded 47 confirmed cases of amatoxin poisoning from accidental consumption of these toxic mushrooms. This outbreak has led to four deaths, and at least four people became so ill that they needed liver transplants.

That is far above what officials normally see. In a typical year, California reports fewer than five poisonings. 

"This is definitely a much larger than usual outbreak. It is lasting longer and going much further into the year than we would have anticipated," Heather Hallen Adams, toxicology chair of the North American Mycological Association, told NBC News.

This outbreak has already reached at least a dozen counties in Northern California and the Central Coast.

Abnormal environmental conditions brought on by above-average precipitation in the spring have led to amatoxin-containing mushrooms blooming beyond normal seasonal expectations across the state.

Western destroying angels typically bloom in the spring, while death caps typically decline by late winter. The resurgence of these poisonous mushrooms into late spring is putting all mushroom foragers at risk.

According to CDPH, these two mushroom varieties have been foraged in neighborhoods, local parks, regional parks, recreation spaces, nature preserves, and at least one national park.

For residents, the pattern is troubling because dangerous mushrooms may appear in many environments where children and pets have access to them.

Amatoxin poisoning is especially dangerous because symptoms often do not appear right away. Researchers found that nausea, vomiting, diarrhea, stomach cramps, and confusion can take anywhere from six to 24 hours to begin. By then, the toxin may already be causing severe liver damage.

The California Poison Control System and state health officials are coordinating the response and statewide case tracking. Officials are also working to make amatoxin poisoning a reportable condition.

For residents, the clearest advice is simple: Do not eat wild mushrooms. If you think you, a child, or a pet may have ingested one, get medical help immediately, even if symptoms have not started. Quick treatment can make a major difference.

Experts say extra caution is the safest move.

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