A longstanding outbreak of Listeria monocytogenes affecting several European countries since 2015 was likely caused by ready-to-eat salmon products, according to the European Safety Authority (EFSA) and the European Centre for Disease Prevention and Control (ECDC).
The outbreak has resulted in 12 cases, including four deaths, across Denmark, France, and Germany as of 8 October, 2018. European health officials used whole genome sequencing to identify the source of the multi-country outbreak, narrowing it down to cold-smoked and marinated salmon products.
The initial cluster of cases was reported in Denmark last August, and was linked to the consumption of ready-to-eat smoked salmon products processed in Poland, Food Ingredients First reported. Health officials enacted control measures, and informed other European countries of the situation at that time.
Meanwhile, France detected the same strain of listeria in marinated salmon products that were also produced by the same Polish processing facility in October 2017. Germany reported the most recent case linked to the outbreak in May 2018.
Due to the lack of whole genome sequencing data from the environmental samples acquired from the Polish processing facility, “It’s currently not possible to confirm whether the contamination occurred in the suspected plant,” according to the EFSA. Further information is needed from the Norwegian primary producers of the contaminated salmon before health authorities can rule out the possibility of contamination at the primary production level.
“It is likely that the extent of this outbreak has been underestimated since the outbreak was identified through sequencing and only a subset of the E.U./E.E.A. countries routinely use this advanced technique to characterize L. monocytogenes isolates,” EFSA said in its technical report surrounding the outbreak. “Although control measures were implemented following the Danish outbreak investigation in September 2017, the identification of the same strain in a salmon product in France and a new human case in Germany suggest that the source of contamination is still active and contaminated products have been distributed to other E.U. countries than Denmark."
New invasive listeriosis cases may arise in Europe until the source of the contamination is eliminated, EFSA said, with “Pregnant women, the elderly and immunocompromised individuals…at increased risk.” Severe clinical course and potentially death are possible outcomes of the illness, the health regulator said.
Image courtesy of the CDC
