Otto Helve

Lyme Borreliosis in Finland, 1995–2014

We investigated the epidemiology of Lyme borreliosis (LB) in Finland for the period 1995–2014 by using data from 3 different healthcare registers. We reviewed data on disseminated LB cases from the National Infectious Diseases Register (21,051 cases) and the National Hospital Discharge Register (10,402 cases) and data on primary LB (erythema migrans) cases from the Register for Primary Health Care Visits (11,793 cases). Incidence of microbiologically confirmed disseminated LB cases increased from 7/100,000 population in 1995 to 31/100,000 in 2014. Incidence of primary LB cases increased from 44/100,000 in 2011 to 61/100,000 in 2014. Overall, cases occurred predominantly in women, and we observed a bimodal age distribution in all 3 registers. Our results clearly demonstrate that the geographic distribution of LB has expanded in Finland and underscore the importance of LB as an increasing public health concern in Finland and in northern Europe in general.

Population-based Borrelia burgdorferi sensu lato seroprevalence and associated risk factors in Finland

Lyme borreliosis (LB) is caused by Borrelia burgdorferi sensu lato (Bb-sl) and is the most common vector-borne disease in Europe. The objectives of this study were to determine the Bb-sl seroprevalence among the general Finnish adult population and to identify risk factors associated with Bb-sl-seropositive status. Two thousand sera from a nationwide health survey from 2011 were tested by whole-cell sonicate IgG ELISA, C6 peptide ELISA, and recomBead IgG 2.0 and test results were linked to a general health questionnaire. A multivariable logistic regression model was used to identify risk factors. The median age of the study population was 56 years (range 29-97) and the Bb-sl weighted seroprevalence was 3.9% (95% confidence interval (CI) 3.03-5.08). The weighted seroprevalence was significantly higher among males than females (adjusted odds ratio 1.91, 95%CI 1.21-3.04). The seroprevalence was highest in Southern, Central, and Eastern regions. The first Bb-sl seroprevalence study in Finland showed a seroprevalence of 3.9% (regional range 0.87%-6.12%). The results of this study can be used, together with previous data on LB incidence and spatial tick distribution, to target public health communication about preventive measures.