Another person has been added to the patient toll in a a deadly outbreak of Listeria monocytogenes infections traced to Dole packaged salads.

There are now 17 people who have been confirmed with the outbreak strain of the pathogen, according to the Centers for Disease Control and Prevention. The sick people live in 13 states with illness onsets ranging from Aug. 14, 2014, through Dec. 30, 2021. Two people have died.

“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,” according to a Feb. 1 outbreak update from the agency.

“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. 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.” 

After the 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 that was produced by Dole.

On Dec. 22, 2021, Dole recalled all Dole-branded and private label packaged salads processed at the two facilities that produced the contaminated packaged salads. On Jan. 7, 2022, Dole recalled additional products containing iceberg lettuce harvested by the contaminated equipment. All of the recalled salads are well past their expiration dates.

“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,” according to the CDC. “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.”

Sick people range in age from 50 to 94 years old, with a median age of 75, and 82 percent are female. Of 15 people with information available, 13 have been hospitalized. Two deaths have been reported from Michigan and Wisconsin.

State and local public health officials are interviewing people, or their family, about the foods they ate in the month before they got sick. Of nine people interviewed, eight reported eating packaged salads. Of the three people who remembered a specific brand, two reported Dole and one reported Little Salad Bar.

About Listeria infections
Food contaminated with Listeria monocytogenes may not look or smell spoiled but can still cause serious and sometimes life-threatening infections. Anyone who has developed symptoms of Listeria infection should seek medical treatment and tell their doctors about the possible Listeria exposure.

Also, anyone who has eaten any of the recalled products should monitor themselves for symptoms during the coming weeks because it can take up to 70 days after exposure to Listeria for symptoms of listeriosis to develop.

Symptoms of Listeria infection can include vomiting, nausea, persistent fever, muscle aches, severe headache, and neck stiffness. Specific laboratory tests are required to diagnose Listeria infections, which can mimic other illnesses.

Pregnant women, the elderly, young children, and people such as cancer patients who have weakened immune systems are particularly at risk of serious illnesses, life-threatening infections, and other complications. Although infected pregnant women may experience only mild, flu-like symptoms, their infections can lead to premature delivery, infection of the newborn, or even stillbirth.

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