In December 2021 the CDC announced an investigation with their public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA) related to a multistate outbreak of Listeria monocytogenes infections.

CDC investigated this outbreak in 2019 and 2020 but was unable to gather enough data to identify the source in the past. CDC reopened the investigation in November 2021 when four new illnesses were reported since the end of August 2021. Epidemiologic and recent laboratory data show that packaged salads produced by Dole are contaminated with Listeria and making people sick.

Eighteen people infected with the outbreak strain of Listeria monocytogenes were reported from 13 states. Illnesses started on dates ranging from August 16, 2014, to January 15, 2022.

Sick people range in age from 50 to 94 years, with a median age of 76, and 83% are female. Of 16 people with information available, all had been hospitalized. Three deaths were reported, one each from Michigan, Ohio, and Wisconsin.

In October 2021, the Georgia Department of Agriculture identified the outbreak strain of Listeria in a Dole brand garden salad as part of a routine sampling program of food at grocery stores. As a result, Dole recalled some of their garden salad products that are now past their “best if used by” dates. This sampling was not part of this outbreak investigation, but WGS later showed that the Listeria bacteria in the garden salad were closely related to the outbreak strain.

After CDC reopened this outbreak investigation, Michigan Department of Agriculture and Rural Development collected samples of packaged salads from retail stores for testing and identified the outbreak strain of Listeria in a Marketside brand package of shredded iceberg that was produced by Dole.

FDA analyzed the positive samples collected by Dole from the harvesting equipment. Results from FDA’s Whole Genome Sequencing (WGS) analysis showed that the strain of Listeria found on the harvesting equipment matched the strain causing illnesses in this outbreak. Dole decommissioned the harvester and it was later dismantled. Product on hold that was included in the December 2021 recall was later tested by Dole and tested positive for the strain of Listeria monocytogenes that caused illnesses in this outbreak.

The investigation was closed on April 4, 2022.