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Research article - Peer-reviewed, 2023

Potential drivers of human tick-borne encephalitis in the orebro region of Sweden, 2010-2021

Kjaer, Lene Jung; Johansson, Magnus; Lindgren, Per-Eric; Asghar, Naveed; Wilhelmsson, Peter; Fredlund, Hans; Christensson, Madeleine; Wallenhammar, Amelie; Bodker, Rene; Rasmussen, Gunlog; Kjellander, Petter


Incidence of tick-borne encephalitis (TBE) has increased during the last years in Scandinavia, but the underlying mechanism is not understood. TBE human case data reported between 2010 and 2021 were aggregated into postal codes within orebro County, south-central Sweden, along with tick abundance and environmental data to analyse spatial patterns and identify drivers of TBE. We identified a substantial and continuing increase of TBE incidence in orebro County during the study period. Spatial cluster analyses showed significant hotspots (higher number of cases than expected) in the southern and northern parts of orebro County, whereas a cold spot (lower number of cases than expected) was found in the central part comprising orebro municipality. Generalised linear models showed that the risk of acquiring TBE increased by 12.5% and 72.3% for every percent increase in relative humidity and proportion of wetland forest, respectively, whereas the risk decreased by 52.8% for every degree Celsius increase in annual temperature range. However, models had relatively low goodness of fit (R-2 < 0.27). Results suggest that TBE in orebro County is spatially clustered, however variables used in this study, i.e., climatic variables, forest cover, water, tick abundance, sheep as indicator species, alone do not explain this pattern.

Published in

Scientific Reports
2023, Volume: 13, number: 1

      SLU Authors

    • UKÄ Subject classification

      Microbiology in the medical area
      Public Health, Global Health, Social Medicine and Epidemiology

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