A total of 18 people infected with the outbreak strain of Listeria monocytogenes were reported from 13 states – Idaho 1, Iowa 2, Maryland 1, Michigan 1, Minnesota 2, Nevada 1, North Carolina 1, Ohio 3, Oregon 1, Pennsylvania 1, Texas 2, Utah 1, and Wisconsin 1. The true number of sick people in an outbreak is likely higher than the number reported, and the outbreak may not have been limited to the states with known illnesses. This is because some people recover without medical care and are not tested for Listeria.
Sick people ranged in age from 50 to 94 years, with a median age of 76, and 83% were female. Of 16 people with information available, all were hospitalized. Three deaths were reported, one each from Michigan, Ohio, and Wisconsin.
Whole genome sequencing (WGS) showed that bacteria from sick people’s samples were closely related genetically. This suggests that people in this outbreak got sick from the same food.
In October 2021, before the most recent CDC investigation began, the Georgia Department of Agriculture identified Listeria in a Dole brand garden salad as part of a routine sampling program of food at grocery stores. WGS later showed that the Listeria in the garden salad was the outbreak strain. The garden salad was produced at Dole’s Bessemer City, North Carolina, facility.
After CDC reopened this outbreak investigation, the 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 lettuce. The shredded iceberg lettuce was produced at Dole’s Yuma, Arizona, facility.
Dole conducted a root cause analysis and collected samples from their facilities and equipment for testing. Dole found Listeria on equipment used to harvest iceberg lettuce. FDA conducted WGS and found that the Listeria on the equipment was the outbreak strain.
Dole’s continued investigation found the outbreak strain on a piece of equipment in their Yuma facility and in packaged salads on hold that were included in the initial recall.
On December 22, 2021, Dole recalled all Dole-branded and private label packaged salads processed at their Bessemer City, North Carolina, and Yuma, Arizona, facilities.
On January 7, 2022, Dole recalled additional products containing iceberg lettuce harvested by the contaminated harvesting equipment.