CDC, public health and regulatory officials in several states and the FDA investigated an outbreak of Salmonella Stanley infections linked to wood ear mushrooms also commonly known as kikurage, dried fungus, or Mu'er/Mu-Er/Mu-Err. On November 4, 2020 the investigation was closed. There were 55 cases reported by 12 states. Six people were hospitalized. There were no deaths. Illnesses started on dates ranging from January 21, 2020 to September 19, 2020.

Epidemiologic and traceback information showed that wood ear mushrooms distributed by Wismettac Asian Foods, Inc. were the likely source of this outbreak. In interviews, ill people answered questions about the foods they ate and other exposures in the week before they became ill. Of 23 people with information, 22 reported eating ramen at a restaurant in the week before their illness started. Several people reported eating at the same ramen restaurants, showing they may have been part of illness clusters. Five illness clusters were identified at restaurants serving ramen in 3 states. Information from restaurants where ill people ate showed that wood ear mushrooms came from Wismettac Asian Foods, Inc. The California Department of Public Health collected dried fungus at one of the restaurants linked to an illness cluster. Testing identified the outbreak strain of Salmonella Stanley in the sample.