2021 Outbreak of Listeria Infections Linked to Packaged Salad Mixes – Investigation Updates
In July 2021, CDC, public health and regulatory officials in several states, and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) began collecting different types of data to investigate a multistate outbreak of Listeria monocytogenes infections.
Epidemiologic, laboratory, and traceback data showed that frozen, fully cooked chicken products supplied by Tyson Foods Inc. made people sick.
As of September 10, 2021, this outbreak is over.
Epidemiologic Data
Three people infected with the outbreak strain of Listeria monocytogenes were reported from two states (see map). Illnesses started on dates ranging from April 6, 2021, to June 5, 2021 (see timeline).
Sick people ranged in age from 60 to 95 years, with a median age of 89, and 66% were male. All three people were hospitalized, and one death was reported from Texas.
State and local public health officials interviewed people about the foods they ate in the month before they got sick. All three people were in a long-term care facility or hospital when they got sick. These facilities served many food items, including meals made with precooked chicken.
Laboratory Data
Public health investigators used the PulseNet system to identify illnesses that were 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 identical. This suggests that people in this outbreak got sick from the same food.
USDA-FSIS found the outbreak strain of Listeria in two samples of fully cooked chicken products during routine product testing.
Traceback Data
USDA-FSIS and state partners collected food purchase records from the long-term care facility and hospital to determine the source of the fully cooked chicken products served. USDA-FSIS also identified the two facilities that produced the fully cooked chicken products found to contain the outbreak strain during routine testing. USDA-FSIS found that the Tyson facility in Dexter, Missouri, produced one of the products that tested positive for the outbreak strain, supplied product to another firm where a positive sample was collected, and distributed fully cooked chicken products to the long-term care facility and the hospital.
Public Health Actions
On July 3, 2021, Tyson Foods Inc. recalled approximately 8,955,296 pounds of ready-to-eat chicken products. Additional products made with Tyson Foods Inc. chicken were recalled on July 8 and July 13, 2021.
Public Health Actions
On July 3, 2021, Tyson Foods Inc., a Dexter, Missouri establishment, is recalling approximately 8,492,832 pounds of ready-to-eat (RTE) chicken products. CDC advises people not to eat, sell, or serve recalled products. See the complete list of recalled products, including product and date codes, on the USDA-FSIS website.
CDC, public health and regulatory officials in several states, and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) are collecting different types of data to investigate a multistate outbreak of Listeria monocytogenes infections.
Epidemiologic and laboratory data show that some precooked chicken products may be contaminated with Listeria and may be making people sick.
Epidemiologic Data
As of July 2, 2021, three people infected with the outbreak strain of Listeria monocytogenes have been reported from two states (see map). Illnesses started on dates ranging from April 6, 2021, to June 5, 2021 (see timeline).
Sick people range in age from 60 to 95 years, with a median age of 89, and 66% are male. All three people were hospitalized, and one death has been reported from Texas.
The true number of sick people in an outbreak is likely higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because some people recover without medical care and are not tested for Listeria. 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 interviewed people about the foods they ate in the month before they got sick. All three people were in a long-term care facility or hospital when they got sick. These facilities served many food items, including meals with precooked chicken.
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 identical. This suggests that people in this outbreak got sick from the same food.
USDA-FSIS found the outbreak strain of Listeria in two samples of precooked chicken products during routine product testing. Along with the epidemiologic data, this suggests that people likely got sick from eating precooked chicken.
USDA-FSIS and state partners are collecting food purchase records from the long-term care facility and hospital to identify a common precooked chicken product that may be making people sick.
Public Health Actions
Until we learn more, CDC is advising people at higher risk for severe Listeria illness and facilities caring for them to take extra precautions: reheat precooked chicken to an internal temperature of 165°F, and do not eat cold dishes made with precooked chicken unless the chicken was reheated before being used in the dish.
