Course of the Salmonella Thompson outbreak
15 August
An increase in the number of Salmonella Thompson cases was noticed in the Salmonella surveillance in the Netherlands. RIVM, the Dutch Food and Merchandise Authority (NVWA) and the relevant municipal health services started an outbreak investigation, while RIVM set up a response team to coordinate the investigation, diagnostics and policy.
1 October
The investigation pinpointed smoked fish as a possible outbreak source. NVWA decided to investigate a fish processing company with a large market share in the Netherlands. Samples of this company’s products tested positive for Salmonella, and all smoked salmon from this producer was recalled. It was discovered soon after this that the strain of Salmonella Thompson found in the smoked salmon was the same as that isolated from patients.
16 October
The source of the contamination proved to be PVC chopping boards used in the Greek branch of the company. The number of patients diagnosed with a Salmonella Thompson infection continued to rise. RIVM warned people who still had smoked salmon of the brand in question in their freezer or refrigerator to throw it away, as it was possibly contaminated.
21 October
RIVM and NVWA agreed to launch a supplemental study to make sure that the new patients had not been infected by other products. RIVM had diagnosed Salmonella Thompson infection in about 850 patients by this time. The supplemental study did not reveal any other sources of infection. The number of new cases detected each week gradually fell/declined.
