Listeria Outbreak Linked to Enoki Mushrooms - November 2022

Outbreak investigation summary

This outbreak is over. Data showed that enoki mushrooms made people in this outbreak sick.

• Two sick people reported eating enoki mushrooms or eating at restaurants with menu items containing enoki mushrooms. Three people did not report eating enoki mushrooms, but two of them reported shopping at grocery stores or eating at restaurants that sell Asian foods.
• The outbreak strains were found in several samples of enoki mushrooms.

Highlights

Although this outbreak investigation has ended, CDC and FDA are working to better understand the risk of Listeria infection from enoki mushrooms.

While CDC and FDA do this work, CDC advises people who are pregnant, aged 65 or older, or have a weakened immune system to not eat raw enoki mushrooms.

• Cook enoki mushrooms thoroughly.
• Keep raw enoki mushrooms separate from foods that won't be cooked.
• Wash your hands, items, and surfaces that have touched raw enoki mushrooms.

Restaurants should cook enoki mushrooms thoroughly before serving to customers and keep raw enoki mushrooms separate from foods that won't be cooked.

This advice is based on the following data:

• Two recent multistate Listeria outbreaks have been linked to enoki mushrooms: this outbreak, and the first known Listeria outbreak in the United States linked to enoki mushrooms in 2020.
• Many samples of enoki mushrooms that were tested in this outbreak investigation were contaminated with Listeria. Some of the samples had large amounts of Listeria.
• More than 20 recalls of enoki mushrooms have been issued since 2020 because of potential Listeria contamination.

Listeria in Enoki Mushrooms

Enoki mushrooms are white and have long, thin stems. They are often sold in a bunch with roots in sealed plastic packaging. They are popular in Japanese, Chinese, and Korean food, and they are almost always eaten cooked in soups, hot pots, and stir-fried dishes.

What people at higher risk should do

Listeria is especially harmful if you are pregnant, aged 65 or older, or have a weakened immune system due to certain medical conditions or treatments. Other people can be infected with Listeria, but they rarely become seriously ill.

If you are pregnant, aged 65 or older, or have a weakened immune system:

• Do not eat recalled or contaminated enoki mushrooms.
  • Throw them away or return them to where you bought them.
• For all other brands of enoki mushrooms, do not eat them raw. Cook them thoroughly.
  • Listeria can grow on foods kept in the refrigerator, but it is easily killed by heating food to a high enough temperature.
• Wash your hands after handling any raw enoki mushrooms.
  • Clean your refrigerator, containers, and surfaces that have touched raw enoki mushrooms.
  • Listeria can easily spread among food, surfaces, and hands.
• Keep raw enoki mushrooms separate from foods that won't be cooked.
  • This prevents the spread of Listeria germs from enoki mushrooms to foods that you won't cook before eating.
• Call your healthcare provider right away if you have any of these symptoms after eating enoki mushrooms:
  • People who are not pregnant usually have fever, muscle aches, and tiredness. They may also get a headache, stiff neck, confusion, loss of balance, or seizures.
  • Pregnant people usually have fever, muscle aches, and tiredness. However, Listeria can cause pregnancy loss or premature birth. It can also cause serious illness or death in newborns.

What restaurants should do

• Do not serve raw enoki mushrooms.
  • Cook enoki mushrooms thoroughly before serving them to customers.
  • Do not use raw enoki mushrooms as garnish.
  • Do not add raw enoki mushrooms on top of soup dishes right before serving. The enoki mushrooms will not get hot enough to kill Listeria germs.
• Keep raw enoki mushrooms separate from foods that won't be cooked.
  • This prevents the spread of Listeria germs from enoki mushrooms to foods that you won't cook before serving to customers.
• Follow FDA's safe handling and cleaning advice if you serve enoki mushrooms.
  • Employees should wash hands after handling raw enoki mushrooms.

About Listeria

• Listeria is especially harmful to pregnant people, adults aged 65 or older, and people with weakened immune systems. This is because Listeria is more likely to spread beyond their gut to other parts of their body, resulting in a severe condition known as invasive listeriosis.
  • For people who are pregnant, Listeria can cause pregnancy loss, premature birth, or a life-threatening infection in their newborn.
  • For people who are 65 years or older or have a weakened immune system, Listeria often results in hospitalization and sometimes death.
• Symptoms usually start within 2 weeks after eating food contaminated with Listeria, but may start as early as the same day or as late as 10 weeks after.
  • Pregnant people usually have fever, muscle aches, and tiredness.
  • People who are not pregnant usually have fever, muscle aches, and tiredness. They may also get a headache, stiff neck, confusion, loss of balance, or seizures.
  • For more information about Listeria, see About Listeria.

See also

• FDA: Outbreak Investigation of Listeria – Enoki Mushrooms
• FDA: Utopia Foods Expands Recall on Enoki Mushrooms
• MD: Consumer Advisory for Enoki Mushrooms
• FDA: Strategy to Help Prevent Outbreaks Associated with Imported Enoki Mushrooms