Federal officials say an outbreak of Listeria infections traced to enoki mushrooms has ended. 

The Centers for Disease Control and Prevention reports that the outbreak sickened five people in four states from coast to coast: California, Nevada, Michigan and New Jersey. No one died, but all five of the patients required hospitalization.  

“The true number of sick people in this 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 or are not tested for Listeria,” according to the CDC.

The Food and Drug Administration says enoki mushrooms distributed by Utopia Foods Inc. of Glendale, NY, and imported from China, and enoki mushrooms labeled as “Producer: Shandong Youhe Biotechnology, Co.,” with an address in China and “Distributed By: Sun Hong Foods, Inc.” are the likely sources of illnesses in this outbreak. 

Enoki mushrooms have become an increasing concern for pubic health officials in recent years. In 2022 they were the single most recalled food in the United States. Because of the dangers of Listeria contamination in enoki mushrooms the CDC is recommending that no one eat them raw. Further, the agency is recommending that no one in high risk groups eat them at all. High risk groups include children, pregnant women, older adults and people with compromised immune systems.

“Many samples of enoki mushrooms were found to be contaminated with various strains of Listeria, including the two outbreak strains. Enumeration (a way to measure how much Listeria is on a food) was conducted for some samples and large amounts of Listeria were found,” according to the CDC outbreak update.

Because of the number of recalls in recent years for imported enoki mushrooms, the FDA has added enoki mushrooms from China to an import alert, basically blocking the importing of those mushrooms. As stated in the import alert, FDA import Divisions may subject shipments of enoki mushrooms from Republic of Korea and China to Detention Without Physical Examination.

“In addition, after a 2020 outbreak linked to enoki mushrooms, FDA began implementing a ‘Strategy to Help Prevent Listeriosis and Salmonellosis Outbreaks Associated with imported Enoki and imported Wood Ear Mushrooms’ to protect public health. This prevention strategy is an affirmative, deliberate approach undertaken by FDA and stakeholders to help limit or prevent future outbreaks linked to certain FDA-regulated foods,” the FDA reported in its outbreak update.

Prior to and during outbreak just ended, multiple state samples have detected Listeria monocytogenes in enoki mushrooms, which led to 18 recalls of them in the U.S. since 2021. Eight of the recalls were linked to enoki mushrooms grown in the Republic of Korea, and 10 from China, were confirmed via labeling, traceback, or whole genome sequencing. 

During this time, FDA sampled and analyzed 127 shipments of enoki mushrooms imported from China and found 18 to be violative, representing a violation rate of more than 14 percent. This effort identified 15 firms with violative products out of at least 37 declared firms that had exported enoki mushrooms from China to the U.S.

In 2020, a deadly outbreak sickened at least 36 people in 17 states, hospitalizing 31 of them. Four people died, and two fetal losses were recorded.

In the outbreak just ended, the CDC reports that sick people’s samples were collected from Oct. 5, 2022, to Feb. 3, 2023.

In November 2021, FDA found Listeria in one sample of enoki mushrooms that they collected at import. The enoki mushrooms were destroyed. The Listeria from this sample was closely related genetically to the Listeria that made the people in this outbreak sick. However, the firm associated with this sample was not identified as a potential source of enoki mushrooms in this outbreak.  

In January 2023, FDA found the outbreak strains of Listeria in an import sample of Utopia Foods brand enoki mushrooms. These enoki mushrooms were imported from China. On Jan. 13, 2023, Utopia Foods expanded their existing recall of enoki mushrooms.

In December 2022, Missouri state officials found one of the outbreak strains of Listeria in a sample of enoki mushrooms produced by Shandong Youhe Biotechnology Co. In January 2023, Maryland Department of Health

found both outbreak strains in two samples of enoki mushrooms produced by the same company in China.

“Although this outbreak investigation has ended, CDC and FDA are working to understand the risk of Listeria contamination in enoki mushrooms,” the CDC reports.