MRSA infections in Norway: A study of the temporal evolution, 2006-2015.

Francesco Di Ruscio,Truls Michael Leegaard,Birgitte Freiesleben De Blasio,Jørgen Vildershøj Bjørnholt,Aina E Fossum Moen

doi:10.1371/journal.pone.0179771

Abstract

BackgroundNorway has one of the lowest prevalences of methicillin-resistant Staphylococcus aureus (MRSA) infections in the world. This study exploits the extensive data on MRSA infections in the Norwegian surveillance system to investigate the important factors defining the MRSA epidemiology.MethodsWe performed a quasi-Poisson regression of the monthly notification rate (NR) of MRSA infections reported from January 2006 to December 2015, comparing the time trend among people with an immigrant vs. Norwegian background and domestic vs. imported infections, stratified by age groups.FindingsA total of 5289 MRSA infections were reported during the study period, of which 2255 (42·6%) were acquired in Norway, 1370 (25·9%) abroad, and 1664 (31·5%) with an unknown place of acquisition. Overall, the monthly NR increased significantly from 2006 to 2015 (+0·8% each month). The monthly increase in immigrants (+1·3%) was steeper than that in people with a Norwegian background (+0·6%). There was a significant growth (+0·4%) in the rate of domestically acquired infections, however, the NR of infections acquired abroad increased faster (+0·8%). For both imported and domestic infections, the increase occurred in persons aged < 70 years.InterpretationOur analysis suggests that immigration and importation, especially among persons aged < 40 years, represent important factors for the increasing notification rate of MRSA infections in Norway.

Highlights

The global spread of methicillin-resistant Staphylococcus aureus (MRSA) over the past 20 years has become a major worldwide public health concern [1,2]
In the present study we investigated the recent trends in MRSA infections by analyzing national registry data between 2006–2015, with a particular emphasis on characterizing the temporal patterns of domestic vs. imported infections, stratified by age, and by Norwegian vs. immigrant background
Our results show that the monthly notification rate of MRSA infections in Norway has increased by a factor of almost three over the last ten years

Summary

Introduction

The global spread of methicillin-resistant Staphylococcus aureus (MRSA) over the past 20 years has become a major worldwide public health concern [1,2]. In Norway, the Netherlands and Sweden, effective surveillance and infection control programs have helped keep the percentage of invasive S. aureus resistant to methicillin below 1% [5]. Recent studies analyzing data until 2011 reported an increase in the incidence and prevalence of MRSA isolates in Norway, which suggests a change in MRSA epidemiology [6,7,8]. We hypothesize that increased international travel, in addition to increased immigration to Norway, may be important drivers for the spread of MRSA through the country and the rise of the prevalence. Norway has one of the lowest prevalences of methicillin-resistant Staphylococcus aureus (MRSA) infections in the world. This study exploits the extensive data on MRSA infections in the Norwegian surveillance system to investigate the important factors defining the MRSA epidemiology

Methods

Results

Conclusion