England’s Food Standards Agency, Food Standards Scotland, Public Health England and Health Protection Scotland issued the joint warning on 3 July, stating: “... Most frozen vegetables, including sweetcorn, need to be cooked before eating. This includes if adding them to salads, smoothies or dips.
“People should always follow manufacturers’ instructions when preparing their food. If the product is not labelled as ‘ready to eat’, the cooking instructions should always be followed before eating the food hot or cold. Frozen sweetcorn is the likely source of an ongoing outbreak of listeriosis affecting five European countries, including the UK.
“Listeriosis is a rare but serious foodborne illness caused by the bacterium Listeria (L) monocytogenes that can be more serious for those individuals who have weakened immune systems and also the elderly, pregnant women and infants.”
The European Food Safety Authority (EFSA) and the European Centre for Disease Prevention and Control (ECDC) have provided an update on the listeriosis outbreak. The health scare has so far affected Austria, Denmark, Finland, Sweden and the UK.
Nine deaths
Experts have used whole genome sequencing to identify the source of contamination, which initially was thought to be limited to frozen corn. As of 8 June 2018, 47 cases, including nine deaths, had been reported.
The same strains of L. monocytogenes were detected in frozen vegetables produced by the same Hungarian company in 2016, 2017 and 2018. This suggested that the strains had persisted in the processing plant despite the cleaning and disinfection procedures that were carried out.
The available information confirmed the contamination at the Hungarian factory. However, further investigations, including thorough sampling and testing, were needed to identify the exact points of environmental contamination at the plant, EFSA and the ECDC said. The same recommendation applied to other companies belonging to the same commercial group if environmental contamination were to be detected, they said.
Immediate recall
On 29 June 2018, the Hungarian Food Chain Safety Office banned the marketing of all frozen vegetable and frozen mixed vegetable products produced by the affected plant between August 2016 and June 2018. It ordered their immediate withdrawal and recall, which it was hoped would be likely to significantly reduce the risk of human infections and contain the outbreak. All freezing activity at the plant has been stopped.
New cases could still emerge, due to 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 recalls and eaten without being cooked properly, according to EFSA and the ECDC.