European Centre for Disease Prevention and Control

Salmonellosis is the second most common foodborne infection in the European Union (EU) with a notification rate of 34.6 cases per 100,000 population in 2006 [1]. The disease mainly causes gastrointestinal symptoms such as fever, diarrhoea, abdominal pain, nausea and vomiting but, depending on the strain and the vulnerability of the host, Salmonella infections can lead to septicaemia and sometimes death. Many efforts are therefore made to reduce the human burden of salmonellosis. As humans generally become infected by eating contaminated and insufficiently cooked food, the efforts are focused on EU-wide implementation of stricter control measures within the animal and food sectors. These have proven to be effective as the notification rates have been decreasing in the EU during the last years [1]. In this week's issue of Eurosurveillance, four European countries present recent outbreaks of Salmonella Typhimurium. S. Typhimurium is one of the two serotypes, the other being S. Enteritidis, accounting for the majority of salmonellosis cases in Europe (70-80% of the cases with known serotypes) [1]. The emergence of multidrug-resistant S. Typhimurium strains, like the definite phage type (DT) 104, in several EU countries is worrying. It is though debatable whether infections with these strains result in higher hospitalisation rates and/or case-fatality rates than infections with other Salmonella strains. In this issue, Doorduyn et al. [2] describes an ongoing S. Typimurium DT104 outbreak in the Netherlands where more than 20% of the cases were hospitalised. Also S. Typhimurium strains fully susceptible to antibiotics can still cause widespread outbreaks. This is presented by Schmid et al. [3], Grandesso et al. [4] and Ethelberg et al. [5] in this issue. These four papers highlight the importance of molecular subtyping in outbreak investigations, which permits to compare strains within and between countries. In the investigations presented, phage typing, Pulsed Field Gel Electrophoresis (PFGE) and Multiple Loci Variable Number of Tandem Repeats Analysis (MLVA) have been used in different combinations. The results show not only that links exist between the countries, as in the outbreaks described by Switzerland [3] and France [4] and some cases in Denmark, which all seem to be caused by the same strain, but that also several outbreaks of the same serotype but different strains may be ongoing in one country simultaneously [2,3,5]. The impact of international food production and trade on infectious diseases is also worth mentioning in this respect. As shown by Schmid et al. [3] …