California’s “Outbreak” of Mushroom Poisonings: Can it Happen Here?

The vast majority of mushrooms are harmless. It’s the few deadly ones that demand respect.”

In 2025, mushroom foraging made national news after four people died in California and dozens were hospitalized from eating poisonous wild mushrooms identified as Amanita phalloides, commonly known as the “death cap.”  Mushroom poisonings happen on the west coast annually, where there is a longer growing season.  But this year was a particularly bad one.  Many people have asked me why, and whether it can that happen here?

Now, first off, I must say that I am the last person to encourage generalized fear of mushrooms, something called “mycophobia.” but in this case there is a reason for it. In several reported cases, the victims were recent immigrants or visitors who mistook the poisonous mushrooms for edible varieties, similar looking to those they are familiar with in their home countries.   

Can this happen here in Manchester by-the-Sea?  Well, in a word, yes, but it is extremely unlikely.  Historically, mushroom poisoning in the U.S. results in very few deaths — on average about three people per year, based on the National Poison Data System data from 2012–2020.

The mushroom responsible for these tragic deaths was Amanita phalloides, the “Death Cap”, which is responsible for over 90% of mushroom fatalities worldwide.  Plenty of mushrooms can get you sick, but relatively few can actually take your life.  These attractive devils grow prolifically in California associated with a type of oak tree.

Amanitas are very effective partners with trees and can often win out when in competition with other fungi.  That is why they have easily spread throughout the world, from pine plantations in Chile all the way to New England, although they are not nearly as prolific here as they are on the west coast.  Interestingly enough, they do not grow anywhere in the Midwest, only on the two coasts.  

Here in Massachusetts, they can also associate with conifers.  For example, just across my street where I found some beautiful specimen in my neighbor’s lawn.  However, those are the only ones I have ever found on Cape Ann in 25 years!

Amanita phalloides are from the same family as the well-known Mario Brothers mushroom, Amanita muscaria, the one with a red cap and white dots all over it.  But that one won’t kill you.  It is simply a strong deliriant, very unpredictable, and more likely to get you sick than silly.

Amanitas are usually the first mushrooms people learn because that genus has more seriously poisonous species than any others and beginners are cautioned to stay away from them.  They are also easy to recognize because they have so many distinctive features including white gills, usually a skirt of tissue on their stem and tufts of tissue on their cap, a fattened or bulbous base at the bottom of their stem, and often a cup of tissue around the stem base.  These are very unique features and finding all of them together is an absolutely means you have an Amanita. Amanita phalloides, specifically, has a smooth greenish to olive-green cap, a large skirt around the stem and a bulbous base.  Their cap color is particularly distinctive, almost unique, a beautiful greenish color.

As I mentioned, I am the last person to encourage generalized fear of mushrooms.  You can pick up, touch and study any mushroom without harm.  Just do not eat them.  However, if you do find this species in your yard, you should remove it and put in the trash to ensure that animals—such as dogs—don’t get poisoned. This is not true about most mushrooms so please do not worry that every mushroom can hurt your pet. Certainly, do not place these into your home’s compost bin, or throw it deeper into the woods where it could spread its spores.

There are over a thousand species of Amanita in North America.  Surprisingly, most of them are edible but a few hundred species are poisonous, therefore it is very important to learn them and to avoid them.  What is insidious about Amanitas is that the poisons within it are not heat labile and cannot be removed by cooking, drying or boiling.

The main poisons, called amatoxins, bind themselves to your RNA stopping protein synthesis and causing cell death.  That’s what happens in your kidneys.  It is a sort of closed cycle that, once in your system, keeps repeating its damage killing cells until it is stopped and that’s a hard job to do.  The symptoms are nefarious because you fall briefly ill within about nine hours but then seem to recover.  Two or three days later, when the poisons have had enough time to get seriously deep in your system, kidney and liver failure can begin to happen and around a third of the time, a kidney transplant or death may occur.  The critical thing to do is to get help early.  And while describing the biology of mushroom poisoning is intense, remember, the actual incidences of US poisonings are exceedingly rare.

Why are so many people drawn to the mystique of mushroom poisonings?  One answer is in history.  Ancient Romans loved eating some of them, but also using them to kill their enemies.  Probably because the conspirators had days to make their escape before the deaths occurred.  Emperor Claudius was killed with them so that Nero could begin his disastrous rule.

Many poisonous Amanita have multiple poisons in them.  A mixture of different amatoxins as well as gastrointestinal poisons and we simply do not know why.  One anecdotal story is how a group of tennis players picked a bunch of pristine white colored mushrooms (Amanitas) growing near the tennis courts to eat.  Some in the group were a bit skeptical so they cooked them first.  The odd thing was that the ones who ate them raw on a salad got quite sick early on, vomiting and therefore removing them from their system.  

The more cautious people who cooked them did not get sick at all until about nine hours later.  Then the serious poisoning sequence began to set in: sickness, recovery, then organ failure.  What they had done by cooking them was to disable the GI irritants in them so that they did not quickly get sick and the amatoxins had a chance to do their job.  A third of that group perished.

The mushrooms responsible for these poisonings were called “Death Angels.”  Also members of the Amanita genus and are completely white from cap to skirt to stem and base.  About five or seven species of Amanita fall under the common name of Death Angels and they grow throughout the US.

One might ask themselves, “Why on earth do these simple creatures develop such an insidious and complex poisons?”  Is it because they don’t want deer to nibble on them?  Like so many other questions concerning fungi, the answer to that question remains a true mystery.

On a more positive note, Amanitas are easy to recognize and often have delightful colors and features.  Just learn to recognize the bad ones and remove them from where pets play.  Keep in mind that the vast majority of mushrooms are not poisonous at all and they certainly are interesting to study.  And you can always access expert help by joining a foraging group or a mycology club.

Gary Gilbert is a member of the Boston Mycological Club, lectures and leads mushroom walks throughout the country. Some of his mushroom recipes are featured in the “Fantastic Fungi Community Cookbook” a compendium of recipes from myco-chefs throughout the country and is the author of “Mycocards”, flashcards for learning mushroom identification (mycocards.com) and resides in Manchester by the Sea.