INDIANAPOLIS — Health officials are investigating after people in different parts of the country got sick with the same strain of Listeria monocytogenes linked to enoki mushrooms.

The Centers for Disease Control and Prevention said data showed that the mushrooms contaminated with Listeria are making people sick, though they are not sure about the specific brand.

So far, only two people have been confirmed to be infected with the outbreak strand, but the CDC believes the true number of sick people is likely higher. 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.

The people who became sick are a 30-year-old man and a 42-year-old man. One is from Michigan while the other is from Nevada. While both men have been hospitalized, no deaths have been reported.

The CDC said the men reported eating enoki mushrooms or eating at restaurants with menu items containing the mushrooms. White with long, thin stems, the mushrooms are often sold in a bunch with roots in sealed plastic packaging. They are popular in Japanese, Chinese and Korean food.

Raw Organic Enoki Mushrooms in a Bunching

The CDC said the outbreak strain was previously found in a sample of enoki mushrooms that the FDA collected at import. However, the firm associated with the sample has not been identified as a potential source of enoki mushrooms in this outbreak.

This is not the first time the CDC has seen Listeria outbreaks with enoki mushrooms. In 2020, the CDC investigated the first known Listeria outbreak in the United States linked to enoki mushrooms. In that outbreak, 36 people were infected in 17 states. Four people died and two people lost their pregnancies.

What is Listeria?

Listeria monocytogenes is a bacterium that can cause the serious infection listeriosis. It can also cause common food poisoning symptoms.

The Centers for Disease Control and Prevention said around 1,600 people get listeriosis every year, resulting in about 260 deaths. It is most likely to sicken pregnant women and their newborns, adults 65 and older and people with weakened immune systems.

What are the symptoms of invasive listeriosis?

Invasive listeriosis happens when the bacteria spread beyond the gut to other parts of the body. Symptoms usually start within two weeks after eating food contaminated with Listeria.

Symptoms in pregnant people are usually mild, with some never showing symptoms. However, the CDC said, infection during pregnancy commonly results in miscarriage, stillbirth, premature delivery, or life-threatening infection in the newborn.

In non-pregnant people, the CDC said, symptoms can be severe, with almost 1 in 20 people with invasive listeriosis dying.

Have there been any recalls?

During the 2020 outbreak, the CDC said there were three recalls. Since then, the FDA has been collecting samples of enoki mushrooms and found Listeria in many samples, resulting in more than 20 recalls.

One recent recall comes from Green Day Produce Inc. in Vernon, California. The FDA reports the company is recalling its 200g/7.05 oz packages of enoki mushrooms sold from September through October 2022 nationwide.

The recall was initiated after testing from the Michigan Department of Agriculture and Rural Development revealed the presence of Listeria. So far, the company does not know of any illnesses reported with their product.

The mushrooms were sold in a clear plastic package with UPC 16430-69080. Anyone with the product is urged to return them to the place of purchase for a full refund.

What should people at higher risk do?

The CDC said Listeria is especially harmful to people who are pregnant, 65 or older, or have a weakened immune system due to certain medical conditions or treatments. People who are pregnant can experience pregnancy loss, premature birth, or life-threatening infection in their newborn. Other people can be infected with Listeria, but they rarely become seriously ill.

If anyone is pregnant, aged 65 or older, or have a weakened immune system they should:

  • Do not eat raw enoki mushrooms. Cook enoki mushrooms thoroughly.
    • Listeria can grow on foods kept in the refrigerator, but it is easily killed by heating food to a high enough temperature.
  • 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 they won’t cook before eating.
  • Wash their hands after handling raw enoki mushrooms.
    • Clean the refrigerator, containers, and surfaces that have touched raw enoki mushrooms.
    • Listeria can easily spread among food, surfaces, and hands.
  • Call their healthcare provider right away if they have any symptoms of severe Listeria illness after eating enoki mushrooms:
    • People who are not pregnant may experience headache, stiff neck, confusion, loss of balance, and convulsions, in addition to fever and muscle aches.
    • Pregnant people usually experience only fever, fatigue, and muscle aches. However, Listeria can cause pregnancy loss or premature birth. It can also cause serious illness or death in newborns.

Additionally, the CDC recommends the following to restaurants

  • 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 they won’t cook before serving to customers.
  • Follow FDA’s safe handling and cleaning advice if they serve enoki mushrooms.
    • Employees should wash their hands after handling raw enoki mushrooms.