This fungi's not fun, guys

This fungi's not fun, guys —

Prized morels are unpredictably and puzzlingly deadly, outbreak report shows.

Mature morel mushrooms in a greenhouse at an agriculture garden in
Zhenbeibu Town of Xixia District of Yinchuan, northwest China's Ningxia
Hui Autonomous Region.

[1]Enlarge / Mature morel mushrooms in a greenhouse at an agriculture
garden in Zhenbeibu Town of Xixia District of Yinchuan, northwest
China's Ningxia Hui Autonomous Region.

True morel mushrooms are widely considered a prized delicacy, often
pricey and surely safe to eat. But these spongey, earthy forest gems
have a mysterious dark side—one that, on occasion, can turn deadly,
highlighting just how little we know about morels and fungi generally.

On Thursday, [2]Montana health officials published an outbreak analysis
of poisonings linked to the honeycombed fungi in March and April of
last year. The outbreak sickened 51 people who ate at the same
restaurant, sending four to the emergency department. Three were
hospitalized and two died. Though the health officials didn't name the
restaurant in their report, state and local health departments at the
time [3]identified it as Dave’s Sushi in Bozeman. The report is
published in the Centers for Disease Control and Prevention's Morbidity
and Mortality Weekly Report.

The outbreak coincided with the sushi restaurant introducing a new
item: a "special sushi roll" that contained salmon and morel mushrooms.
The morels were a new menu ingredient for Dave's. They were served two
ways: On April 8, the morels were served partially cooked, with a hot,
boiled sauce poured over the raw mushrooms and left to marinate for 75
minutes; and on April 17, they were served uncooked and cold-marinated.

The mystery poison worked fast. Symptoms began, on average, about an
hour after eating at the restaurant. And it was brutal. "Vomiting and
diarrhea were reportedly profuse," the health officials wrote, "and
hospitalized patients had clinical evidence of dehydration. The two
patients who died had chronic underlying medical conditions that might
have affected their ability to tolerate massive fluid loss."

Of the 51 sickened, 46 were restaurant patrons and five were employees.
Among them, 45 (88 percent) recalled eating morels. While that's a high
percentage for such an outbreak investigation, certainly enough to make
the morels the prime suspect, the health officials went further. With
support from the CDC, they set up a matched case-control study, having
people complete a detailed questionnaire with demographic information,
food items they ate at the restaurant, and symptoms.

Mysterious poison

Forty-one of the poisoned people filled out the questionnaire, as did
22 control patrons who ate at the restaurant but did not report
subsequent illness. The analysis indicated that the odds of recalling
eating the special sushi roll were nearly 16 times higher among the
poisoned patrons than among the controls. The odds of reporting any
morel consumption were nearly 11 times higher than controls.

The detailed consumption data also allowed the health officials to
model a dose response, which suggested that with each additional piece
of the special roll a person recalled eating, their odds of sickness
increased nearly threefold compared with people who reported eating
none. Those who ate four or more pieces of the roll had odds nearly
22.5 times higher. A small analysis focusing on the five employees
sickened, which was not included in the published study but was noted
by the Food and Drug Administration, echoed the dose-response finding,
indicating that sickness was linked with larger amounts of morel
consumption.

When the officials broke down the analysis by people who ate at the
restaurant on April 17, when the morels were served uncooked, and those
who ate at the restaurant on April 8, when the mushrooms were slightly
cooked, the cooking method seemed to matter. People who ate the
uncooked rather than the slightly cooked mushrooms had much higher odds
of sickness.

This all strongly points to the morels being responsible. At the time,
the state and local health officials engaged the FDA, as well as the
CDC, to help tackle the outbreak investigation. But [4]the FDA reported
that "samples of morel mushrooms collected from the restaurant were
screened for pesticides, heavy metals, toxins, and pathogens. No
significant findings were identified." In addition, the state and local
health officials noted that DNA sequencing identified the morels used
by the restaurant as Morchella sextelata, a species of true morel. This
rules out the possibility that the mushrooms were look-alike morels,
called "false morels," which are known to contain a toxin called
gyromitrin.

The health officials and the FDA tracked down the distributor of the
mushrooms, finding they were cultivated and imported fresh from China.
Records indicated that 12 other locations in California also received
batches of the mushrooms. Six of those facilities responded to
inquiries from the California health department and the FDA, and all
six reported no illnesses. They also all reported cooking the morels or
at least thoroughly heating them.
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References

1. https://cdn.arstechnica.net/wp-content/uploads/2024/03/GettyImages-1230560442-scaled.jpeg
2. https://www.cdc.gov/mmwr/volumes/73/wr/mm7310a1.htm?s_cid=mm7310a1_w
3. https://dphhs.mt.gov/News/2023/July/FinalSummaryonMorelMushroomsFoodbourneOutbreak
4. https://www.fda.gov/food/outbreaks-foodborne-illness/investigation-illnesses-morel-mushrooms-may-2023
5. https://arstechnica.com/science/2024/03/deadly-morel-mushroom-outbreak-highlights-big-gaps-in-fungi-knowledge/2/
6. https://arstechnica.com/science/2024/03/deadly-morel-mushroom-outbreak-highlights-big-gaps-in-fungi-knowledge/2/