A total of 42 people infected with the outbreak strain of Listeria monocytogenes were reported from 21 states. Illnesses started on dates ranging from August 17, 2018, to March 13, 2025. Of 42 people with information available, 41 were hospitalized. A total of 14 deaths were reported from 9 states: California, Illinois, Indiana, Michigan, Minnesota, North Carolina, New York, Tennessee, Texas, and Washington. Most people in this outbreak reported living in long-term care facilities or were hospitalized prior to becoming sick.

CDC investigated this outbreak in 2018, 2021, and 2023. Epidemiologic data in previous investigations identified that sick people were residents in long-term care facilities and nursing homes and the likely source was a food served in those types of institutions, but there was not enough information to identify a specific food. CDC reopened the investigation in October 2024 after six new illnesses were reported. In February 2025 after traceback identified a product of interest, the outbreak strain was found in environmental samples from Prairie Farms. 

State and local public health officials interviewed people about the foods they ate in the month before they got sick. Of 42 people with information, 38 (90%) reported living in long-term care facilities or were hospitalized before becoming sick. Nine people reported mechanical soft diets, including foods like supplement shakes. Information provided by facilities showed at least 4 people drank the recalled supplement shakes. Additionally, facilities confirmed that supplement shakes were available to residents.

FDA traced food records from long-term care facilities. These records showed that supplement shakes made by Prairie Farms were a common food served at the long-term facilities. On February 4, 2025, FDA conducted an onsite inspection and collected environmental samples at Prairie Farms for testing. On February 19, 2025, WGS showed that the Listeria in the environment were closely related to the bacteria from sick people.