Comparison of the number of Lyme neuroborreliosis cases in European Centre for Disease Prevention and Control (ECDC) data and national public surveillance reports, 2018-2023.

Lyme borreliosis (LB) is the most common vector-borne disease in Europe. At least 29 European Economic Area (EEA) countries publish online LB surveillance reports. However, countries have different criteria for what is notifiable for LB surveillance, limiting comparability. EEA countries began reporting Lyme neuroborreliosis (LNB) cases, a disseminated LB manifestation, to the European Centre for Disease Prevention and Control (ECDC) in 2018, using a uniform case definition. This analysis compared LNB data from ECDC and national surveillance reports to evaluate their utility in monitoring LB in Europe. LNB surveillance data from 2018 to 2023 were downloaded from ECDC. Nationally reported online LB surveillance data from EEA countries were identified and reviewed. Countries that reported LNB cases in national surveillance and to ECDC were included and case data were compared. Of 31 EEA countries during 2018 to 2023, 11 (35 %) differentiated LNB cases in their national published LB surveillance; eight of these also reported to ECDC. The number of LNB cases published in national reports in these eight countries did not exactly match the number of LNB cases reported to ECDC but overall disease trends were similar. Comparing the LNB cases from eight countries in ECDC and national surveillance demonstrates that both capture evolving LNB disease trends despite some differences in the number of cases reported to each. To allow for more robust comparisons of LB burden and trends across Europe, harmonizing case definitions and reporting mechanisms for LB would provide great value.