Estimation of medically-attended LB incidence in Norway, Finland and Poland using data from national surveillance and published literature

• Estimation of medically-attended LB incidence by clinical manifestation in Norway, Finland and Poland using national surveillance data and published literature. • Incidence of medically-attended LB in Norway was 213.2 / 100,000, 116.4 / 100,000 in Finland and 130.9 / 100,000 in Poland. • 67,578 annual cases were estimated in the three countries which is 2.7 times more than reported by public surveillance. • Disseminated LB was 9.9, 36.3 and 6.2/ 100,000 in Norway, Finland and Poland respectively corresponding to a total of 4920 annual cases. Lyme borreliosis (LB) is the most common tick-borne disease in Europe. Many European countries conduct LB surveillance, but these data do not always capture the complete burden on the healthcare system and are difficult to compare across countries due to unstandardized reporting procedures. In this study, we combined data from public health surveillance and published literature to estimate the incidence of patients with LB seeking healthcare by clinical manifestation in Norway, Finland, and Poland. Surveillance data in each country were combined with medical administrative datasets (e.g., public health registries, claims databases, electronic medical records) to estimate the incidence of medically-attended LB. These estimates were adjusted to exclude cases that were not prescribed LB-specific antibiotics, and remove cases present in multiple datasets. Country-specific distributions of clinical manifestations were used to obtain medically-attended incidence by clinical manifestation. We estimated a high incidence of medically-attended LB in Norway (213.2 / 100,000 population per year [PPY]), Finland (116.4 / 100,000 PPY), and Poland (130.9 / 100,000 PPY). This corresponds to 67,578 annual cases or 2.7 times more than reported by surveillance in these countries. Incidence of disseminated LB was also substantial with 9.9, 36.3 and 6.2/ 100,000 PPY in Norway, Finland and Poland respectively corresponding to a total of 4,920 annual cases. This study provides estimates for incidence of medically-attended LB, including disseminated LB, in three European countries and highlights the limitations of surveillance data alone in assessing LB burden.