Listeria monocytogenes Outbreak 

Linked to Ready-to-Eat Chicken

Outbreak Investigation After Action Review, Report 2021-08

Highlights

• Close collaboration among public health 

partners led to a recall 11 days after initial 

outbreak notification.

• Whole genome sequencing (WGS) of isolates 

generated by the U.S. Department of 

 griculture’s ood afety and nspection ervice 

(FSIS) routine sampling provided investigators 

with key data, highlighting the importance of 

these analyses to generate hypotheses and 

inform outbreak investigations. 

• Ill people in this outbreak were unable to provide specific details on what they ate 

before getting sick, but all ate meals at institutions. Menus from these institutions 

proved to be useful in gathering epidemiologic evidence and guiding traceback.

State of residence of people infected with Listeria monocytogenes

Outbreak at a Glance

Illnesses 3

States included 2

Hospitalizations 3

Deaths 1

Response at a Glance

Recall or Public Health 

Alert Yes
What Happened?

From June 24 to July 22, 2021, public health 

officials in multiple States, the Centers for 

Disease Control and Prevention (CDC), and 

FSIS investigated an outbreak of three Listeria 

monocytogenes (Lm) illnesses linked to readyto-eat (RTE) chicken. All ill people ate their 

meals at institutions before getting sick and 

limited exposure information was available. 

Investigators used institution menus to gather details on foods ill people may have 

eaten.

The three clinical Lm isolates were genetically indistinguishable from two RTE chicken 

isolates collected by FSIS from two different federally inspected establishments during 

routine testing. Investigation revealed that one of these establishments (Establishment 

A) supplied RTE chicken to the other establishment. Further investigation identified that 

Establishment A also supplied RTE chicken to the institutions where ill people had 

eaten. Strong WGS evidence and traceback data led Establishment A to conduct a 

recall of approximately 8.9 million pounds of RTE chicken 11 days after initial outbreak 

notification.

What we Learned from this Outbreak

Communication

 lose communication, coordination, and data sharing between , 

 , tate public health partners, and industry facilitated the rapid 

response to this outbreak ontinuing to foster relationships with public 

health partners will enable to quickly respond to future outbreaks 

FSIS Routine Sampling and Whole Genome Sequencing

 routine sampling is important both to ensure that ederal 

establishments are producing safe products in sanitary environments, 

and to provide data on -regulated products and establishments to 

 ’s ulse et database enetic data from isolates collected as part 

of routine sampling are uploaded to ulse et, allowing investigators to 

compare these isolates to other food, animal, environmental, and 

clinical samples When an outbreak is detected, such data can provide 

epidemiologists with key clues to generate hypotheses, guide 

investigations, and solve outbreaks quickly to prevent further illnesses 
What Can You Do to Prevent or Solve the Next 

Outbreak?

Helpful Links

• FSIS Recall 023-2021, July 3, 2021

• CDC Food Safety Alert, final update September 10, 2021

• CDC Listeria Prevention

• Report a Problem with Food

• ore information about ’ response to foodborne outbreaks

 f you think you have a 

foodborne illness, see a 

health care provider for 

treatment Your health 

care provider can test you 

and, if the tests show you 

have a reportable 

foodborne illness, your 

 tate or local public health 

officials should be notified 

 f you suspect a food 

product made you sick, 

report the problem to 

 or the appropriate 

public health agency 

Consumers

Lm can grow and persist

in environments (e g ,

drains) where other 

pathogens typically do 

not isruptions to the 

production environment, 

like during construction, 

may allow Lm to spread 

to other areas of a 

production facility 

 roducers of 

products should have 

robust plans for 

identifying and controlling 

Lm to ensure they are 

complying with the 

regulatory requirements 

of the Listeria rule. 

 ecommendations for 

establishments that 

produce post-lethality 

exposed products

can be found in the 

compliance guideline for 

controlling Lm 

Industry

 ontinue to work closely 

with local, tate, and 

 ederal partners to 

detect and investigate 

outbreaks mail 

 oodborne isease epor

ts@usda gov to notify 

 if -regulated 

products may be 

involved in an outbreak 

Public Health Partners