Multi-Country Outbreak of Listeria Monocytogenes Tied to Frozen Vegetables

The European Center for Disease Prevention and Control (ECDC) has announced that frozen corn and other frozen vegetables have been linked with the Listeria monocytogenes outbreak that has been occurring in 5 European nations since 2015.

As of June 8, 2018, 47 cases of listeriosis cases have occurred, resulting in 9 deaths. The source of the outbreak was initially attributed to frozen corn but through whole genome sequencing it has been determined that there were matching strains of Listeria monocytogenes found in other frozen vegetables as well that had been produced 2016 to 2018 by a Hungarian facility.

Greenyard, a Belgium-based vegetable supplier has suspended activity at their Hungarian facility in Baja and the Hungarian Food Chain Safety Office has banned marketing of frozen vegetables produced by the company between August 2016 and June 2018. As a result of the ban, Greenyard has issued a recall of products including frozen corn, peas, beans, spinach, and sorrel made at the Baja plant between August 13, 2016, and June 20, 2018.

As part of the investigation, health officials interviewed patients with confirmed listeriosis infections. Eleven of the 26 interviewed patients confirmed consumption of corn either frozen or nonfrozen. From the other 15 patients, 6 reported consuming frozen mixed vegetables, 6 were unsure if they had consumed corn or mixed vegetables, and 3 patients reported that they had not consumed either corn or mixed vegetables.

“The same strains of L. monocytogenes have been detected in frozen vegetables produced by the same Hungarian company in 2016, 2017 and 2018,” The European Food Safety Authority (EFSA) announced in a statement, “This suggests that the strains have persisted in the processing plant despite the cleaning and disinfection procedures that were carried out.”

Common symptoms providers should be cognizant of include high temperature, muscle pain, diarrhea, chills, and vomiting. Populations with a higher vulnerability include pregnant women, newborn babies, people over 65 years of age, and people with weakened immune systems.

Health authorities are hopeful that the recall will reduce the risk of infection, but new cases could still occur due to the long shelf-life of frozen products and the lengthy incubation period of listeriosis, which is up to 70 days. The EFSA and ECDC call for avoidance of the recalled product and for all European consumers to thoroughly cook frozen vegetables, including products that do not require cooking, such as salad or smoothie ingredients.

The joint report produced by the EFSA and ECDC indicate that the next steps in the investigation will include sampling and testing to identify the precise point of contamination in the Hungarian facility.

For the most recent case counts associated with the Listeria monocytogenes outbreak in Europe, be sure to check out the Contagion® Outbreak Monitor.