Population-based seroprevalence of Puumala hantavirus in Finland: smoking as a risk factor.

Puumala hantavirus (PUUV) causes hemorrhagic fever with renal syndrome in humans, that is an endemic disease in Finland. We estimated the seroprevalence of PUUV in Finland and explored risk factors and disease associations by using unique survey data with health register linkage. A total of 2000 sera from a nationwide health survey from 2011, representative of the adult population, were screened for PUUV IgG by immunofluorescence assay. We performed statistical analysis adjusting for stratified cluster design and taking into account sampling weights. In total, 254 sera among 2000 tested were PUUV-IgG-positive resulting in a weighted seroprevalence of 12.5%, (95% CI 10.9-14.4), mirroring known age and regional variation in reported incidence. No associations between PUUV-seropositivity and chronic diseases including cardiovascular (including hypertension), pulmonary, kidney disease and cancer were observed. Smoking was significantly associated with seropositivity (adjusted OR 1.54; 95% CI 1.16-2.04). In addition, significant dose-response relations were found for the number of cigarettes smoked daily (OR 1.14; 95% CI 1.12-1.28). The results are important for disease burden assessment and guide intervention strategies, highlighting also the role of smoking prevention.