Federal officials say a three-year Listeria outbreak caused by mushrooms imported from the Republic of Korea appears to be over.

The implicated enoki mushrooms from H&C Food Inc., Guan’s Mushroom Co. and Sun Hong Foods Inc. are past their shelf life and should not be available for sale, according to an outbreak updat the U.S. Centers for Disease Control and Prevention posted today.

Public health officials in Michigan, California and other states worked with the CDC to use DNA fingerprinting on samples from patients and mushrooms. The outbreak strain of Listeria monocytogenes was found in two samples of mushrooms collected from a grocery store by Michigan officials. An outbreak patient reported eating mushrooms from the store before becoming ill. The California Department of Public Health collected enoki mushrooms from grocery stores and identified the outbreak strain in one sample.

FDA collected samples of enoki mushrooms for testing at import from Green Co. LTD of the Republic of Korea. On April 6, 2020, results showed that two samples yielded the outbreak strain of Listeria monocytogenes. As a result, on April 7, 2020, FDA placed Green Co. LTD on an import alert, meaning their product can be stopped at the U.S. border.

Having been determined to have begun in November 2016, the CDC reports the outbreak lasted through December 2019.

“As of June 9, 2020, this outbreak appears to be over. Epidemiologic, traceback, and laboratory evidence showed that enoki mushrooms supplied by Green Co. LTD, located in the Republic of Korea, were the likely source of this outbreak,” according to the outbreak update. “. . . enoki mushrooms supplied by Green Co. LTD, located in the Republic of Korea, were the likely source of this outbreak.”

A total of 36 people have been identified so far as having been sickened in the outbreak. The patients are from 17 states. Almost all patients — 31 of the 33 with information available — were so sick they had to be admitted to hospitals. Four patients died. Six pregnancy-associated cases were reported, with two resulting in fetal loss.

Ill people ranged in age from less than 1 to 96 years old, with a median age of 67, according to the CDC. Fifty-eight percent of ill people were women.

On March 18, 2020, the Korean Ministry of Food and Drug Safety published its investigation findings and steps it will take to prevent future illnesses. It found Listeria monocytogenes in enoki mushrooms produced by two firms in the Republic of Korea.