RESEARCH PAPER
Temporal trends in Lyme borreliosis and tick-borne encephalitis in Nordic countries, 2018-2024: a descriptive epidemiological analysis of European surveillance data
1
Department of (Clinical) Epidemiology and Global Health, Utrecht University, Utrecht, the Netherlands
Submission date: 2026-02-20
Final revision date: 2026-03-21
Acceptance date: 2026-03-30
Online publication date: 2026-04-22
Corresponding author
Gurkeerat Gill
Department of (Clinical) Epidemiology and Global Health, Utrecht University, Heidelberglaan 6, 3584 CS Utrecht, the Netherlands
Department of (Clinical) Epidemiology and Global Health, Utrecht University, Heidelberglaan 6, 3584 CS Utrecht, the Netherlands
KEYWORDS
TOPICS
ABSTRACT
Background:
Tick-borne diseases are the fastest-growing vector-borne infections in northern Europe, yet no comprehensive multi-country analysis of Lyme borreliosis (LB) and tick-borne encephalitis (TBE) trends across the Nordic countries using standardized post-2018 European surveillance data has been published.
Material and methods:
Annual case counts were extracted from the European Center for Disease Prevention and Control (ECDC) Surveillance Atlas for LB (Denmark, Norway) and TBE (all four countries). Descriptive time-series analysis included year-over-year changes, compound annual growth rates (CAGR), crude incidence rates, and pre- versus post-COVID-19 comparisons.
Results:
Over seven years, 3,118 LB and 4,344 TBE cases were reported. Denmark showed the most rapid growth for both LB (CAGR +19.1%) and TBE (CAGR +30.8%). Combined Nordic TBE burden increased 37.2% (2018-2024), with post-COVID-19 annual cases exceeding pre-pandemic levels by 57.7%. Peak regional TBE case count occurred in 2023 (898 cases).
Conclusions:
Both diseases show escalating trends with substantial inter-country variation. These findings establish pre-vaccine baselines for LB, strengthen the case for expanding TBE vaccination, and highlight critical surveillance gaps – particularly the absence of ECDC-reported LB data for Sweden and Finland.
Tick-borne diseases are the fastest-growing vector-borne infections in northern Europe, yet no comprehensive multi-country analysis of Lyme borreliosis (LB) and tick-borne encephalitis (TBE) trends across the Nordic countries using standardized post-2018 European surveillance data has been published.
Material and methods:
Annual case counts were extracted from the European Center for Disease Prevention and Control (ECDC) Surveillance Atlas for LB (Denmark, Norway) and TBE (all four countries). Descriptive time-series analysis included year-over-year changes, compound annual growth rates (CAGR), crude incidence rates, and pre- versus post-COVID-19 comparisons.
Results:
Over seven years, 3,118 LB and 4,344 TBE cases were reported. Denmark showed the most rapid growth for both LB (CAGR +19.1%) and TBE (CAGR +30.8%). Combined Nordic TBE burden increased 37.2% (2018-2024), with post-COVID-19 annual cases exceeding pre-pandemic levels by 57.7%. Peak regional TBE case count occurred in 2023 (898 cases).
Conclusions:
Both diseases show escalating trends with substantial inter-country variation. These findings establish pre-vaccine baselines for LB, strengthen the case for expanding TBE vaccination, and highlight critical surveillance gaps – particularly the absence of ECDC-reported LB data for Sweden and Finland.
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