Imported methicillin-resistant Staphylococcus aureus, Sweden.

Countries such as Sweden that have a low prevalence of methicillin-resistant Staphylococcus aureus (MRSA) offer the opportunity to discern and study transmission of imported cases of MRSA. We analyzed 444 imported cases of MRSA acquisition reported in Sweden during 2000-2003. Risk for MRSA in returning travelers ranged from 0.1 (95% confidence interval [CI] 0.01-0.4) per 1 million travelers to Nordic countries to 59.4 (95% CI 44.5-79.3) per 1 million travelers to North Africa and the Middle East. Most imported cases (246, 55%) were healthcare acquired, but regions with the highest risk for MRSA in travelers showed a correlation with community acquisition (r = 0.81, p = 0.001). Characteristic differences in MRSA strains acquired were dependent on the region from which they originated and whether they were community or healthcare acquired. Knowledge of differences in transmission of MRSA may improve control measures against imported cases.

Epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in Sweden 2000-2003, increasing incidence and regional differences.

BACKGROUND: The occurrence of methicillin-resistant Staphylococcus aureus (MRSA) has gradually become more frequent in most countries of the world. Sweden has remained one of few exceptions to the high occurrence of MRSA in many other countries. During the late 1990s, Sweden experienced a large health-care associated outbreak which with resolute efforts was overcome. Subsequently, MRSA was made a notifiable diagnosis in Sweden in 2000. METHODS: From the start of being a notifiable disease in January 2000, the Swedish Institute for Infectious Disease Control (SMI) initiated an active surveillance of MRSA. RESULTS: The number of reported MRSA-cases in Sweden increased from 325 cases in 2000 to 544 in 2003, corresponding to an overall increase in incidence from 3.7 to 6.1 per 100,000 inhabitants. Twenty five per cent of the cases were infected abroad. The domestic cases were predominantly found through cultures taken on clinical indication and the cases infected abroad through screening. There were considerable regional differences in MRSA-incidence and age-distribution of cases. CONCLUSION: The MRSA incidence in Sweden increased over the years 2000-2003. Sweden now poises on the rim of the same development that was seen in the United Kingdom some ten years ago. A quarter of the cases were infected abroad, reflecting that international transmission is now increasingly important in a low-endemic setting. To remain in this favourable situation, stepped up measures will be needed, to identify imported cases, to control domestic outbreaks and to prevent transmission within the health-care sector.