Four people have died and three others have required liver transplants after eating the aptly named death cap mushroom that is proliferating in California following a rainy winter.

The California Department of Public Health is urging people to avoid mushroom foraging altogether this year because death cap mushrooms are easily confused with safe, edible varieties.

Since Nov. 18 there have been more than three dozen cases of death cap poisonings reported, including the four deaths and three liver transplants, according to the health department. Many who sought medical attention suffered from rapidly evolving acute liver injury and liver failure. Several patients required admission to an intensive care unit. They have ranged in age from 19 months to 67 years old.

The death cap is one of the most poisonous mushrooms in the world and is part of a small group of mushrooms containing amatoxins, which are highly potent compounds causing 90% of fatal mushroom poisonings globally. They are in city parks and in forests, often under oak trees.