Emergence of new Salmonella Enteritidis phage types in Europe? Surveillance of infections in returning travellers

Abstract

Background: Among human Salmonella Enteritidis infections, phage type 4 has been the dominant phage type in most countries in Western Europe during the last years. This is reflected in Salmonella infections among Swedish travellers returning from abroad. However, there are differences in phage type distribution between the countries, and this has also changed over time.

Methods: We used data from the Swedish infectious disease register and the national reference laboratory to describe phage type distribution of Salmonella Enteritidis infections in Swedish travellers from 1997 to 2002, and have compared this with national studies conducted in the countries visited.

Results: Infections among Swedish travellers correlate well with national studies conducted in the countries visited. In 2001 a change in phage type distribution in S. Enteritidis infections among Swedish travellers returning from some countries in southern Europe was observed, and a previously rare phage type (PT 14b) became one of the most commonly diagnosed that year, continuing into 2002 and 2003.

Conclusions: Surveillance of infections among returning travellers can be helpful in detecting emerging infections and outbreaks in tourist destinations. The information needs to be communicated rapidly to all affected countries in order to expedite the implementation of appropriate investigations and preventive measures.

Figure 1

Incidence rates (IR) of Salmonella Enteritidis infections among Swedish travellers to Spain, Greece and Turkey. Country specific annual incidence rate of Salmonella Enteritidis per 100,000 air travellers from Sweden. Incidence rates are calculated based on the number of cases notified to the Swedish infectious Disease register using the number of flight passengers from Sweden to the first foreign destination as the denominator.

Figure 2

Distribution of phage types of Salmonella Enteritidis cases notified in Sweden, 1997 to 2002.

Figure 3

Dominant phage types of Salmonella Enteritidis infections among Swedish travellers according to country visited. Only countries with more than 10 reported cases and phage types accounting for > 25 % of all cases are shown. a) 1997 – 2000 b) 2001

Figure 4

Notified cases of Salmonella Enteritidis PT 14b among Swedish travellers by country of infection, 1997 – 2002.