Incidence of Lyme Borreliosis in Europe from National Surveillance Systems (2005-2020)

Abstract

Background: Lyme borreliosis (LB) is the most common tick-borne disease in Europe. To inform European intervention strategies, including vaccines under development, we conducted a systematic review for LB incidence. Methods: We searched publicly available surveillance data reporting LB incidence in Europe from 2005 to 2020. Population-based incidence was calculated as the number of reported LB cases per 100,000 population per year (PPY), and high LB risk areas (incidence >10/100,00 PPY for 3 consecutive years) were estimated. Results: Estimates of LB incidence were available for 25 countries. There was marked heterogeneity in surveillance systems (passive vs. mandatory and sentinel sites vs. national), case definitions (clinical, laboratory, or both), and testing methods, limiting comparison across countries. Twenty-one countries (84%) had passive surveillance; four (Belgium, France, Germany, and Switzerland) used sentinel surveillance systems. Only four countries (Bulgaria, France, Poland, and Romania) used standardized case definitions recommended by European public health institutions. Among all surveillance systems and considering any case definition for the most recently available years, national LB incidences were highest in Estonia, Lithuania, Slovenia, and Switzerland (>100 cases/100,000 PPY), followed by France and Poland (40-80/100,000 PPY), and Finland and Latvia (20-40/100,000 PPY). Incidences were lowest in Belgium, Bulgaria, Croatia, England, Hungary, Ireland, Norway, Portugal, Romania, Russia, Scotland, and Serbia (<20/100,000 PPY). At the subnational level, highest LB incidences (>100/100,000 PPY) were observed in areas of Belgium, Czech Republic, France, Germany, and Poland. Overall, on average 128,888 cases are reported annually. An estimated 202/844 million (24%) persons in Europe reside in areas of high LB incidence and 202/469 million (43.2%) persons reside in areas of high LB incidence among countries with surveillance data. Conclusion: Our review showed substantial variability in reported LB incidence across and within European countries, with highest incidences reported from the Eastern, Northern (Baltic states and Nordic countries), and Western Europe surveillance systems. Standardization of surveillance systems, including wider implementation of common case definitions, is urgently needed to interpret the range of differences in LB incidence observed across European countries.

Keywords: Europe; Lyme borreliosis; epidemiology; incidence; surveillance.

FIG. 1.

Incidence^a of LB from national surveillance networks (2005–2019). ^aNumber of LB cases per 100,000 PPY, shown in logarithmic scale base 2 for comparison. ^bFrom sentinel surveillance data. Vertical lines show 95% CIs for extrapolated data. Gaps in data occur when no data reported for year(s). LB case definitions changed in Scotland in 2012–2013 (to not require laboratory confirmation) and in Poland in 2005 (to reflect EUCALB and U.S. CDC case definitions). Switzerland stopped reporting LB surveillance data in 2014. The United Kingdom and Ireland data are derived ad hoc from routine surveillance data from each of the individual constituent countries. Tabulated data are provided in Supplementary Table S2. CDC, U.S. Centers for Disease Control and Prevention; CI, confidence interval; EUCALB, European Concerted Action on Lyme Borreliosis; LB, Lyme borreliosis; PPY, population per year.

FIG. 2.

Incidence^a (cases per 100,000 PPY) of LB overall by country from national surveillance networks in Europe (A) for the national average and (B) for the subnational level (when data available). *Maps represent national surveillance data available for European countries, based on our search methodology. ^aWeighted mean for most recent 3-year period available (all case definitions).