Epidemiological update: Multistate outbreak of Salmonella Stanley infectionsArchived
In July 2012, the European Centre for Disease Prevention and Control initiated a Europe-wide investigation on a Salmonella Stanley outbreak, together with the affected Member States, the European Food Safety Authority (EFSA) and the European Reference Laboratory for Salmonella (EURL Salmonella). Cases were associated with strains showing an indistinguishable PFGE pattern not previously reported in Europe.
Epidemiological and microbiological outbreak investigation at the European level
Between July and September 2012, ECDC encouraged European Union (EU) and European Economic Area (EEA) Member States to perform Xbal-PFGE typing on all S. Stanley human isolates. The image profile of the outbreak strain was shared with all EU countries. ECDC collected and analysed molecular typing data on S. Stanley from EU/EEA Member States to explore potential sources of infection within the food production chain in this multi-country outbreak.
Following the publication of the joint ECDC/EFSA rapid risk assessment on 21 September 2012, ECDC suggested to the EU/EEA Member States to perform PFGE typing only on a subset of isolates, and to report to ECDC on a monthly basis the number of non-travel associated S. Stanley cases, regardless of travel history within or outside the EU (possible outbreak related cases). The objective of this update is to monitor the evolution of the outbreak. Although the case definition for this monitoring purpose is broader than during the intensive phase of the outbreak (higher sensitivity), the epicurve is providing an indication of the development of the outbreak. ECDC will provide a monthly update of the situation in the EU/EEA until the outbreak is considered over.
Ten EU Member States have had cases with PFGE results matching the PFGE outbreak profile. These countries were asked to provide the number of non-travel related cases of S. Stanley identified per month between 1 August 2011 and 23 November 2012.
From 2007 to 2011, an average of nine cases of non-travel related S. Stanley infections were reported monthly to the European Surveillance System (TESSy) from the EU/EEA Member States.
Epidemiological update
Between 1 August 2011 and 23 November 2012, 611 cases of non-travel-related S. Stanley infections (probable and confirmed cases*) were identified in the EU: Hungary (212), Austria (186), Germany (68), Belgium (37), United Kingdom (35), Czech Republic (31), Sweden (17), Italy (14), Slovakia (10), and Greece (1) (Figure 1).
* See case definition at the end of the document
Figure 1: Distribution of cases of non-travel-related Salmonella Stanley infections (probable and confirmed cases*) by Member States and month of report, August 2011 – November 2012 (as of 23 November) (n=611)
The number of cases reported is decreasing consecutively in September and October. The number of cases identified in November is currently an underestimation, due to the delay in serotyping and reporting at national level.
Microbiological update
Comparative molecular epidemiological analyses of human, food, animal and environmental isolates’ PFGE fingerprints performed by ECDC and the EURL Salmonella corroborate the available epidemiological evidence. This provides additional evidence that strongly supports the conclusions of the ECDC/EFSA rapid risk assessment of 21 September 2012, in particular the implication of the turkey production chain as the probable main source of the outbreak.
Conclusions
The number of cases represented in this update provides an indication of the trend of the outbreak. Despite the decrease in number of cases in September and October, the number of non-travel related cases reported these two months exceeds the background level. Therefore the outbreak cannot yet be considered as over. Additional cases are expected in November due to reporting delays. ECDC will continue to monitor the situation.
The conclusions and recommendations of the joint ECDC/EFSA rapid risk assessment published on 21 September 2012 remain unchanged.
* EU epidemic case definition for Salmonella Stanley multi-country outbreak Confirmed case A laboratory confirmed case of Salmonella Stanley with PFGE pattern matching the ‘Belgium outbreak strain’AND Onset of symptoms after August 2011AND Without travel history outside the EU in 1–7 days prior the onset of symptomsProbable caseA laboratory confirmed case of Salmonella Stanley, no PFGE available AND Onset of symptoms after August 2011AND Without travel history outside the EU in 1–7 days prior the onset of symptoms.Exclusion criteria If the Salmonella Stanley strain has a different PFGE profile it should be excluded.
