European officials have linked ready-to-eat products containing cucumbers to a multi-country outbreak of Salmonella that has sickened 147 people.

The European Centre for Disease Prevention and Control (ECDC) and European Food Safety Authority (EFSA) said five countries are affected: Denmark, Finland, Germany, Ireland and the United Kingdom.

Behind the UK, which has 129 of the Salmonella Agona outbreak cases, is Finland with 15 cases. Denmark, Germany and Ireland have had one case each. The confirmed Irish case had a travel history to the UK prior to onset of symptoms.

A total of 122 cases have been recorded since January 2017. The other 25 infections occurred between 2014 and 2016. One patient with several underlying illnesses died.

Experts from EFSA and ECDC believe ready-to-eat products containing cucumbers and prepared in the UK may be the source of the Salmonella. However, they could not identify the specific point in the production chain where contamination took place.

The ECDC warned new outbreak cases may occur with a “high likelihood” that the outbreak strains will re-emerge in early 2019, as seen in the seasonal occurrence of cases in previous years.

The outbreak was first detected in the UK using whole genome sequencing (WGS). Cases peaked in April 2017 and 2018. Seventeen Salmonella Agona food isolates from this year, detected in the UK, were closely genetically related to the human strains. Eleven of the isolates were isolated from cucumbers sampled during processing before and after washing. The other six were found in ready-to-eat food products containing cucumbers .

Epidemiological investigations in other affected countries did not generate any strong hypothesis about the vehicle or source of the Salmonella.

“At present, there is insufficient epidemiological information available on the consumption of contaminated products by humans to support the microbiological evidence provided by the isolation of the outbreak strain in food,” said ECDC.

Although cucumbers used in all of the contaminated finished product samples came from Spain, between November 2017 and April 2018, no connection between supply chains was identified. Primary producers of cucumbers were different and they were delivered to different processing companies through different distributors in the UK.

Laboratory results for Salmonella in all cucumber samples, taken at primary production level in Spain or during distribution to/within UK, were negative.

Salmonella Agona is the 10th most commonly reported Salmonella serotype in the European Surveillance System (TESSy). From 2012 to 2016, Salmonella Agona was reported by 26 EU countries with an annual case number ranging from 378 to 582. The UK, Germany and France accounted for the highest proportions of confirmed cases.

During 2007-2016 in the EU, Salmonella Agona accounted for 13 outbreaks responsible for 636 cases and 12 hospitalizations, but no deaths were reported.

Symptoms of Salmonella infection usually appear 12-72 hours after the pathogen enters the body and include fever, abdominal pain, diarrhea, nausea and sometimes vomiting. The illness usually lasts four to seven days in otherwise healthy adults. High-risk groups, which include children, pregnant women, the elderly and people such as cancer patients who have weakened immune systems, can develop life-threatening symptoms.

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