martes, 7 de octubre de 2014
Initial contamination remains unknown in largest ever Dutch Salmonella outbreak.
In total 1,149 cases were laboratory-confirmed between August and December 2012
On 15 August 2012, an increase in the number of Salmonella Thompson cases was noticed by the Salmonella surveillance in the Netherlands. A case–control study was performed, followed by a food investigation.
In total 1,149 cases were laboratory-confirmed between August and December 2012 of which four elderly (76–91 years) were reported to have died due to the infection. The cause of the outbreak was smoked salmon processed at a single site.
The smoked salmon had been continuously contaminated in the processing lines through reusable dishes, which turned out to be porous and had become loaded with bacteria. This is the largest outbreak of salmonellosis ever recorded in the Netherlands.
The temporary closure of the processing site and recall of the smoked salmon stopped the outbreak. An estimated four to six million Dutch residents were possibly exposed to the contaminated smoked salmon and an estimated 23,000 persons would have had acute gastroenteritis with Salmonella Thompson during this outbreak.
This outbreak showed that close collaboration between diagnostic laboratories, regional public health services, the national institute for public health and the food safety authorities Although a case–control study was started immediately after detection of the outbreak, it took several weeks before the cause could be identified.
The main reason for the delay was the low number of cases in the beginning of the outbreak and the low number of completed questionnaires, from cases and controls, available for analysis.
A number of other possible sources were suggested before the analysis led to salmon. This was most likely caused by the relatively low number of cases reporting consumption of smoked fish (62/108, 57%). This can be due to recall bias, but also because the salmon was incorporated in other products, for example pre-sale ready-to-eat salads or as part of a menu in the catering industry.