Week-old speculation about frozen corn being responsible for a three-year listeriosis outbreak in Europe, which has had an 18.75  percent fatality rate, is probably correct.

The European Food Safety Authority (EFSA) and the European Centre for Disease Prevention and Control (ECDC) jointly published a rapid outbreak assessment today (March 22) that says frozen corn  is the “likely source of an outbreak of Listeria monocytogenes” involving Austria, Denmark, Finland, Sweden, and the United Kingdom since 2015.

The five European unio (EU) countries have reported 32 confirmed listeriosis cases with six deaths between December 2015 and March 8 this year, according to the EFSA-ECDC assessment. Whole genome sequencing was used to define the multi-country outbreak of Listeria monocytogenes serogroup IVb multi-locus sequence type 6. Investigators also used it to identify the implicated food source.

Other current listeriosis outbreaks in Australia, South Africa, and Europe are not related events.

Investigations point toward frozen corn packed in Poland and processed and produced in Hungary. The report recommends further investigation to identify the exact point of contamination in the food chain.

Food business operators in Poland, Finland, Sweden and Estonia have withdrawn and recalled the implicated products. These measures are likely to reduce the risk of human infections in these countries.

However, new cases may be identified due to the long incubation period of listeriosis, which is up to 70 days, the long shelf-life of frozen corn, and the possible future consumption of frozen corn bought before the recall was implemented.

To reduce the risk of Listeria monocytogenes infection from frozen corn, consumers should adequately heat frozen vegetables to kill pathogens. This applies especially to consumers at the highest risk of contracting listeriosis – such as the elderly, pregnant women, newborns, and adults with weakened immune systems.

What is a rapid outbreak assessment?
Coordination across the EU is crucial when there are multi-country foodborne outbreaks. One aspect of this coordination is the production of a rapid outbreak assessment (ROA) by EFSA and ECDC in close cooperation with affected countries.

The ROA gives an overview of the situation in terms of public health and identifies the cause of the infections. It also includes trace-back and trace-forward investigations to identify the origin of the outbreak and wher contaminated products have been distributed. These help to identify measures that will prevent further spread of the outbreak.