Nine people have died due to a Listeria monocytogenes outbreak, with experts warning that new cases may yet emerge.
As of 8 June 2018 and since 2015, 47 cases have been confirmed as part of the recent Listeria monocytogenes outbreak, which has been sweeping Austria, Denmark, Finland, Sweden and the UK.
The European Food Safety Authority (EFSA) and the European Centre for Disease Prevention and Control (ECDC) have identified the likely source as frozen corn and other frozen vegetables produced in a company in Hungary.
How has Hungary responded to the Listeria monocytogenes outbreak?
On 29 June 2018, the Hungarian Food Chain Safety Office banned the marketing of all frozen vegetables and frozen mixed vegetables produced by the company between August 2016 and June 2018.
It also ordered their immediate withdrawal and recall, with all freezing activity at the plant terminated in June 2018.
These actions are expected to significantly reduce the risk of human infections, but in an updated risk assessment, EFSA and the ECDC have warned that new cases may still emerge as long as contaminated products are still on the market and in consumers’ freezers.
New cases could be brought on by:
- The long incubation period of listeriosis (up to 70 days);
- The long shelf life of frozen corn products; and
- The consumption of frozen corn bought before the recall and eaten without being properly cooked.
Any contaminated vegetables from the 2017 and 2016 production seasons also pose a risk to consumers until the completion of the withdrawal and recall.
What advice has been given to consumers?
The ECDC and EFSA’s risk assessment recommends that consumers thoroughly cook frozen vegetables that are not labelled as ready-to-eat in order to reduce the risk of Listeria monocytogenes infection. This includes vegetables that can be consumed without cooking, for example in salads and smoothies.
Consumers at the highest risk of contracting listeriosis – for instance the elderly, pregnant people, and people with weakened immune systems – have been warned to especially heed this advice.
Initially, it was thought that frozen corn was the sole food source of the Listeria monocytogenes outbreak, but the use of whole-genome sequencing found matching strains of the bacteria in other frozen vegetables produced by the Hungarian company in 2016, 2017 and 2018.
This suggests that the strains have persisted in the processing plant despite the cleaning and disinfection procedures that were carried out. The ECDC and EFSA are now calling for further investigations, including thorough sampling and testing, to identify the exact points of contamination.