A team of scientists from the Netherlands public health and food safety authorities have published a detailed report of an outbreak of Salmonella Thompson infection that affected at least 1,149 people, including four deaths, between August and December 2012.
The outbreak was detected when routine Salmonella surveillance showed an increase in the number of cases of Salmonella Thompson infection in mid-August. Case-control studies and food investigations identified a link between the cases and smoked salmon processed at a single site.
Further investigation revealed that the smoked salmon had been continuously contaminated during processing by reusable dishes, which were in fact porous and had become heavily contaminated over time. The cleaning and sanitisation procedures applied to the dishes were not sufficient to remove contamination before reuse.
The authors of the report comment that this was the largest Salmonella outbreak ever recorded in the Netherlands and suggest that the confirmed cases represent only a small fraction of the people affected. They estimate that four to six million Dutch residents could have been exposed to the contaminated salmon and that 23,000 people could have become ill as a result.
The report is published in the online journal Eurosurveillance and can be found in full here.