Experts from the European Centre for Disease Prevention and Control (ECDC) and the European Food Safety Authority said they believed products prepared in the UK were the source of the outbreak. However, they added that the source of contamination had not yet been pinpointed.
The ECDC report added: “Further investigations along the food chain are needed to identify the source of contamination.
“These should include collection of information about various production and processing stages for the ready-to-eat products implicated in this event, as well as thorough sampling and testing.”
New outbreak cases
The health bodies warned that until the specific point of contamination along the food production chain has been identified and controlled, new outbreak cases might occur in early 2019.
Illness caused by salmonella
“Most persons infected with salmonella develop diarrhoea, fever, and abdominal cramps in 12–36 hours after infection.
“The illness usually lasts 4 to 7 days. Although most people recover without treatment, severe infections may occur. Infants, elderly persons, immune-compromised persons are more likely than others to develop severe illness.”
The outbreak was first detected in the UK using whole genome sequencing (WGS), with the genetic makeup of samples of salmonella taken from each of the five affected countries all being very similar.
Cases peaked in April 2017 and 2018. The close genomic relationship and the distinct seasonal spring peaks suggest that cases are part of an intermittent common source outbreak.
122 cases of salmonella
So far, there have been 122 cases of salmonella reported since 1 January 2017 and 25 historical cases between 2014 and 2016. The UK has reported the most cases (129), followed by Finland (15), Germany (1) and Ireland (1).
Earlier this year, a report for the ECDC found that salmonella cases had increased by 3% across the EU since 2014, with more than 94,000 human cases of salmonellosis reported in 2016. Salmonella bacteria were the most common cause of foodborne outbreaks (22.3%), up 11.5% compared with 2015, according to the data.
The recall of several batches of frozen vegetables by Greenyard UK earlier this month followed a Europe-wide outbreak of food poisoning caused by Listeria monocytogenes that has been going on for years. The strain of listeria, which has been traced to a plant in Hungary also by means of WGS, has caused 47 reported cases of illness so far, with nine of those proving fatal.
Meanwhile, dairy processor Danone has launched an investigation into claims that its infant formula milk Aptamil has made a number of babies ill.
Food Standards agency comment
A Food Standards Agency spokesman told Food Manufacture it was working with Public Health England to narrow down the likely source of a reoccurring Salmonella Agona outbreak in the UK and Europe.
“Evidence produced through whole genome sequencing of human cases suggests there is a link between a batch of cucumbers used in ready to eat products which may have been contaminated at a stage in the production chain," said the spokesman.
“Use of these specific cucumbers had already stopped before their identification as the suspected source and there has been a significant reduction in cases.
“We recommend people should take simple steps to stop themselves getting ill, including washing fruit and vegetables, cooking food thoroughly and washing hands before you prepare, cook or eat food.”