Montana public health officials investigated an outbreak of foodborne illness associated with Dave's Sushi in Bozeman. Implicated meal dates ranged from March 28 and April 17, 2023. Fifty-one individuals reported becoming sick with gastrointestinal symptoms after eating at the restaurant. Two of these individuals died and 3 were hospitalized. Most individuals became ill within 3 hours following their meal at the restaurant. Diarrhea, nausea, vomiting, and abdominal pain were among the most common symptoms of the reported cases.

The Gallatin City-County Health Department (GCCHD) and the Montana Department of Public Health and Human Services (MT DPHHS) conducted a case-control study. Results indicated that consuming morel mushrooms at the restaurant was strongly associated with developing gastrointestinal illness. Additionally, individuals who reported consuming a greater quantity of sushi containing morels were more likely to develop illness compared to those who reported consuming fewer pieces.

MT DPHHS and GCCHD worked with the FDA to perform testing on food samples. DNA sequencing of morel mushrooms collected from the restaurant identified the species as Morchella sextelata, a type of true morel. Samples were screened for pesticides, heavy metals, bacterial toxins, and pathogens. No significant findings were identified.

A subset analysis compared illness from dining at the restaurant on April 8, when the morels reportedly underwent some cooking process by being marinated in a sauce immediately after the sauce had been boiled, and April 17, when the morels were uncooked and marinated in a sauce that had not been boiled. Consumption of morels on both dates was associated with developing illness. However, consumption of morels was more strongly associated with developing illness on April 17, when the morels were reported prepared without any cooking process.

Health department sanitarians traced the morels to a single importer, and a separate distributor that supplied mushrooms to multiple states. The morel mushrooms were cultivated and imported fresh from China.