Investigation Details
Posted December 13, 2023
This outbreak is over. Learn what you can do to protect yourself from getting sick from Salmonella.
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 Thompson infections.
Epidemiologic, laboratory, and traceback data showed that onions processed at Gills Onions were contaminated with Salmonella and made people sick.
Epidemiologic Data
As of December 4, 2023, a total of 80 people infected with the outbreak strain of Salmonella were reported from 23 states (see map). Illnesses started on dates ranging from August 2, 2023, to November 11, 2023 (see timeline). Of the 72 people with information available, 18 (25%) were hospitalized. One death from Wisconsin was reported.
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.
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.
The table below has information about sick people in this outbreak (“n” is the number of people with information available for each demographic).
| Demographics | Information |
|---|---|
| Age (n=80) |
Range from <1 to 90 years Median age of 42 years |
| Sex (n=80) |
60% Female 40% Male |
| Race (n=65) |
92% White 6% African American/Black 2% Asian |
| Ethnicity (n=64) |
89% non-Hispanic 11% Hispanic |
State and local public health officials interviewed people about the foods they ate in the week before they got sick. Of 32 people with information available, 27 (84%) reported eating or likely eating onions or were served diced onions. Of these 27 people, 7 people resided in long-term care facilities. Investigators identified an illness sub-cluster of three people who resided in the same long-term care facility. Investigating a sub-cluster can sometimes help identify a food item eaten by all the sick people that could be the source of the outbreak.
Laboratory and Traceback Data
Public health investigators used the PulseNet system to identify illnesses that may have been 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 were closely related genetically. This suggested that people in this outbreak got sick from the same food.
The outbreak strain was identified by FDA in October 2023 in environmental samples collected from the farm where the onions were grown. Other Salmonella strains were also identified from samples taken from the onion farm. CDC identified people who got sick with these strains of Salmonella, but there was not enough epidemiologic or traceback evidence to confirm these illnesses were part of the outbreak.
WGS analysis of bacteria from 78 people’s samples and one environmental sample did not predict resistance to any antibiotics. More information is available at the National Antimicrobial Resistance Monitoring System (NARMS) site.
FDA conducted a traceback investigation and determined that onions processed at Gills Onions were available at points of service where people ate prior to becoming ill. Meal records from the long-term care facilities showed that people were served diced onions from Gills Onions.
Public Health Actions
On October 23, 2023, Gills Onions recalled fresh diced onion products.
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 Thompson infections.
Epidemiologic and traceback data show that onions processed at Gills Onions may be contaminated with Salmonella and may be making people sick.
Epidemiologic Data
As of October 24, 2023, a total of 73 people infected with the outbreak strain of Salmonella have been reported from 22 states (see map). Illnesses started on dates ranging from August 2, 2023, to September 25, 2023 (see timeline). Of the 65 people with information available, 15 (23%) have been hospitalized. No deaths have been reported.
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.
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.
The table below has information about sick people in this outbreak (“n” is the number of people with information available for each demographic).
| Demographics | Information |
|---|---|
| Age (n=73) |
Range from <1 to 90 years Median age of 41 years |
| Sex (n=73) |
58% Female 42% Male |
| Race (n=59) |
93% White 5% African American/Black 2% Asian |
| Ethnicity (n=58) |
88% non-Hispanic 12% Hispanic |
State and local public health officials are interviewing people about the foods they ate in the week before they got sick. Of 19 people with information available, 14 (74%) reported eating onions or being served diced onions. Of these 14 people, 6 people reside in long-term care facilities. Investigators identified a sub-cluster of three people who reside in the same long-term care facility. Investigating a subcluster can sometimes help identify a food item eaten by all the sick people that could be the source of the outbreak.
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.
FDA conducted a traceback investigation and determined that onions processed at Gills Onions were available at points of service where people ate prior to becoming ill. Meal records from the long-term care facilities showed that people were served diced onions from Gills Onions.
WGS analysis of bacteria from 71 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.
Public Health Actions
On October 24, 2023, Gills Onions recalled fresh diced onion products. CDC is advising people to check their freezers and to not eat any recalled diced onions. Businesses should not sell or serve recalled Gill’s Onions products or use recalled onion products in other foods.
