Lyme Neuroborreliosis-Significant Local Variations in Incidence within a Highly Endemic Region in Sweden.

The aim of this study was to perform a detailed epidemiological overview of Lyme neuroborreliosis (LNB) 2008-2021 in a highly Lyme borreliosis-endemic area in Sweden using a geographic information system (GIS). Diagnosis of LNB was based on clinical symptoms and analysis of cerebrospinal fluid (CSF) according to European guidelines. From laboratory databases and medical records, we detected all patients with CSF pleocytosis and intrathecal anti- Borrelia antibody production and listed clinical features. The distribution of LNB cases within Kalmar County, Sweden was investigated using GIS. In total, 272 cases of definite LNB were confirmed with an average yearly incidence of 7.8/100,000. Significant differences in incidence were noted between children 0-17 years (16/100,000) and adults 18+ years (5.8/100,000) ( p < 0.001), between rural (16/100,000) and urban areas (5.8/100,000) ( p < 0.001) and between selected municipalities ( p < 0.001). Distinct clinical differences in presentation of LNB were also noted between children and adults. Thus, the incidence of LNB varies significantly locally and in relation to age, and clinical presentation shows differences between children and adults. Surveillance of LNB and knowledge of local epidemiological conditions may facilitate preventive measures.