2022 Salmonella Outbreak Linked to Alfalfa Sprouts – Investigation Details
Posted February 28, 2023
CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA) collected different types of data to investigate a multistate outbreak of Salmonella Typhimurium infections.
Epidemiologic and traceback data showed that SunSprout Enterprises raw alfalfa sprouts were the source of this outbreak.
As of February 28, 2023, this outbreak is over.
Epidemiologic Data
A total of 63 people infected with the outbreak strain of Salmonella Typhimurium were reported from eight states (see map).
Public health officials collected many different types of information from sick people, including their age, race, ethnicity, other demographics, and the foods they ate in the week before they got sick. This information provided clues to help investigators identify the source of the outbreak.
Illnesses started on dates ranging from December 2, 2022, to February 2, 2023 (see timeline). Sick people ranged in age from less than one to 83 years, with a median age of 42, and 61% were female. Of 43 people with race and ethnicity information, 42 are White and 1 is African American/Black; No one reported Hispanic ethnicity. Of 59 people with information available, 10 were hospitalized.
The true number of sick people in this outbreak was likely much higher than the number reported, and the outbreak may not have been limited to the states with known illnesses. This is because many people recover without medical care and are not tested for Salmonella.
State and local public health officials interviewed people about the foods they ate in the week before they got sick. Of the 50 people interviewed, 35 (70%) reported eating alfalfa sprouts. This percentage was significantly higher than the 8.7% of respondents who reported eating sprouts in the FoodNet Population Survey—a survey that helps estimate how often people eat various foods linked to diarrheal illness. This difference suggests that people in this outbreak got sick from eating alfalfa sprouts.
Laboratory and Traceback Data
Public health investigators used the PulseNet system to identify illnesses that may be part of this outbreak. CDC PulseNet manages a national database of DNA fingerprints of bacteria that cause foodborne illnesses. DNA fingerprinting is performed on bacteria using a method called whole genome sequencing (WGS).
WGS showed that bacteria from sick people’s samples are closely related genetically. This suggests that people in this outbreak got sick from the same food.
WGS analysis of bacteria from 63 people’s samples did not predict resistance to any antibiotics. Standard antibiotic susceptibility testing by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory is currently underway.
FDA’s traceback evidence indicated that the restaurants and grocery stores identified in this outbreak received raw alfalfa sprouts from SunSprout Enterprises. Additionally, eight of the individuals identified in this outbreak confirmed they had purchased Sun Sprouts-brand alfalfa sprouts from local grocery stores.
Public Health Actions
On December 29, 2022, SunSprout Enterprises recalled four lots of raw alfalfa sprouts, lot numbers 4211, 5211, 3212, and 4212. The sprouts were distributed to food service and grocery customers in Nebraska, Kansas, and Iowa between late November and mid-December 2022. Recalled sprouts had best-by dates between 12/10/2022 and 1/7/2023.
CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA) are collecting different types of data to investigate a multistate outbreak of Salmonella Typhimurium infections.
Epidemiologic and traceback data show that alfalfa sprouts may be contaminated with Salmonella and may be making people sick.
Epidemiologic Data
As of December 29, 2022, a total of 15 people infected with the outbreak strain of Salmonella have been reported from three states (see map). Illnesses started on dates ranging from December 2, 2022, to December 13, 2022 (see timeline).
Public health officials collect many different types of information from sick people, including their age, race, ethnicity, other demographics, and the foods they ate in the week before they got sick. This information provides clues to help investigators identify the source of the outbreak.
Sick people range in age from 19 to 78 years, with a median age of 39, and 67% are female. Of 14 people with information available, two have been hospitalized.
The true number of sick people in this outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because many people recover without medical care and are not tested for Salmonella. In addition, recent illnesses may not yet be reported as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak.
State and local public health officials are interviewing people about the foods they ate in the week before they got sick. Of the 12 people interviewed, all (100%) reported eating alfalfa sprouts. This percentage was significantly higher than the 8.7% of respondents who reported eating sprouts in the FoodNet Population Survey—a survey that helps estimate how often people eat various foods linked to diarrheal illness. This difference suggests that people in this outbreak got sick from eating alfalfa sprouts.
Laboratory and Traceback Data
Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. CDC PulseNet manages a national database of DNA fingerprints of bacteria that cause foodborne illnesses. DNA fingerprinting is performed on bacteria using a method called whole genome sequencing (WGS).
WGS showed that bacteria from sick people’s samples are closely related genetically. This suggests that people in this outbreak got sick from the same food.
WGS analysis of bacteria from 15 people’s samples did not predict resistance to any antibiotics. Standard antibiotic susceptibility testing by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory is currently underway.
FDA’s preliminary traceback evidence indicates that the restaurants and grocery stores identified in this outbreak received alfalfa sprouts from SunSprout Enterprises. Additionally, two of the individuals identified in this outbreak confirmed they had purchased Sun Sprouts brand alfalfa sprouts from their local grocery store.
Public Health Actions
On December 29, 2022, SunSprout Enterprises recalled four lots of raw alfalfa sprouts, lot numbers 4211, 5211, 3212, and 4212. The sprouts were distributed to food service and grocery customers in Nebraska, Kansas, and Iowa between late November and mid December 2022. Recalled sprouts have best-by dates between 12/10/2022 and 1/7/2023.
CDC advises people to not eat, sell, or serve recalled raw alfalfa sprouts.
