Epidemiology and Infection

Original Papers

Salmonella, Campylobacter

A long-lasting outbreak of Salmonella Typhimurium U323 associated with several pork products, Denmark, 2010

K. G. KUHNa1 c1, G. SØRENSENa2, M. TORPDAHLa3, M. K. KJELDSENa3, T. JENSENa4, S. GUBBELSa1a5, G. O. BJERAGERa4, A. WINGSTRANDa2, L. J. PORSBOa2 and S. ETHELBERGa1a3

a1 Department of Epidemiology, Statens Serum Institut, Copenhagen, Denmark

a2 Department of Microbiology and Risk Assessment, National Food Institute, Technical University of Denmark, Copenhagen, Denmark

a3 Department of Microbiology Surveillance and Research, Statens Serum Institut, Copenhagen, Denmark

a4 Danish Veterinary and Food Administration, Copenhagen, Denmark

a5 European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control, Stockholm, Sweden

SUMMARY

This paper shows that control of foodborne disease outbreaks may be challenging even after establishing the source of infection. An outbreak of Salmonella Typhimurium U323 infections occurred in Denmark from March to September 2010, involving 172 cases. Before the detection of human cases, several positive isolates of the outbreak strain had been found in a particular pig slaughterhouse and thus early traceback, investigation and control measures were possible. Several batches of pork and pork products were recalled and the slaughterhouse was closed twice for disinfection. No single common food item was identified as the outbreak source, but repeated isolation of the outbreak strain from the slaughterhouse environment and in pork and products as well as patient interviews strongly suggested different pork products as the source of infection. Furthermore, a matched case-control study identified a specific ready-to-eat spreadable pork sausage (teewurst) as the source of a sub-outbreak (matched odds ratio 17, 95% confidence interval 2·1–130).

(Received October 06 2011)

(Revised March 12 2012)

(Accepted March 26 2012)

(Online publication April 26 2012)

Key words

  • Epidemiology;
  • foodborne infections;
  • outbreaks;
  • Salmonella (Typhimurium);
  • Salmonella typing

Correspondence:

c1 Author for correspondence: Ms. K. G. Kuhn, Department of Epidemiology, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark. (Email: KUH@ssi.dk)

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