Undercooked mushrooms served at Montana restaurant tied to outbreak that left two diners dead and dozens ill

The CDC said that further research needs go into morel mushrooms and the impact they can have on humans

Two people passed away and over 50 people fell ill after undercooked morel mushrooms inside sushi rolls were served at a Montana restaurant, leading to a gastrointestinal illness outbreak last year.

The Centres for Disease Control and Prevention released a report last week detailing how two diners had died, likely as a result of eating undercooked morel mushrooms.

Morel mushrooms are generally considered edible, and only rare cases of illnesses have been reported after they were eaten. But the CDC said that little is known about the human health effects of these specific fungi.

In the report, the CDC said that between March and April 2023, 51 people had reported gastrointestinal illnesses after eating at a restaurant in Bozeman, Montana, that had to temporarily shut its doors after the outbreak.

The restaurant was identified as Dave’s Sushi by a state report obtained by CNN.

In a statement on their social media in April 2023, Dave’s Sushi said that they “understand that several of our customers who dined with us on Monday, April 17, 2023 became ill. We believe that the common ingredient that may have been consumed was FDA-inspected, cultivated morel mushrooms used in Monday’s special roll.”

The 51 people experienced a range of symptoms, from mild to severe, which resulted in three hospitalisations and two people losing their lives.

The two people were separately dining at the restaurant, but both experienced severe nausea, vomiting and diarrhoea and had symptom onset within an hour of eating their meals.

Both of them also had chronic underlying medical conditions that might have affected their ability to withstand the huge fluid loss, the CDC said.

After the restaurant temporarily closed and underwent an inspection, the Montana Department of Public Health and Human Services and Montana’s Gallatin City-County Health Department worked with the CDC to conduct a study among the restaurant-goers to find the source of the outbreak.

The health authorities found that the two deceased people had eaten a special sushi roll that contained salmon and morel mushrooms.

The morels were a new addition to the menu and the only ingredient unique to the special sushi roll — allowing the authorities to make the mushrooms a suspect of the outbreak very early on.

The mushrooms were served in differing ways on different occasions, at one point, they were served partially cooked by pouring a hot boiled sauce over the raw morels and letting them marinate for 75 minutes.

On another occasion, the morels were served uncooked and cold-marinated, the CDC said.

The health authority said that the likely source of this outbreak was uncooked or undercooked mushrooms served at the Montana restaurant in their sushi rolls.

Multiple violations were also spotted at the restaurant during an inspection on 18 April, such as temperature control issues and improper time control, sanitation and storage of personal items.

Out of the 51 cases who fell ill, 45 people reported eating the morels during their meal out.

The morels were traced back to a single importer, which cultivated and imported the mushrooms from China.

The health authorities contacted facilities in California that also use the same morel mushrooms from the importer and said they had not received any complaints of illness from people who ate the morels at their establishments.

What they did say, however, was that they all cooked or thoroughly heated the morels before they dished them up.

Aaron Parker, the owner of Dave’s Sushi, spoke to CBS in December and said he carried out his own investigation to try and find the safest way to cook the mushrooms.

He even contacted other chefs and found that many, like himself, were surprised to learn about the toxins in morels.

"They had no idea that morel mushrooms had this sort of inherent risk factor regardless of preparation," Mr Parker said to the outlet.

The restaurant stopped serving morels and the CDC added that their investigation highlighted gaps in how much people know about morels and their toxins, and more research should be carried out to understand how they affect human health.

In a release in May last year while the investigation was ongoing, Dave’s Sushi also said that “no matter the circumstances or the findings, our hearts go out to the loved ones of the two people who passed away and to all who have been impacted.”

“Moving forward, we want to bring attention to the potential risks of incorporating morel mushrooms in recipes,” they added. “Our goal is to help prevent a situation like this from happening again to anyone.”

The Independent has contacted Dave’s Sushi for comment.