Geo-Spatial Characteristics of 567 Places of Tick-Borne Encephalitis Infection in Southern Germany, 2018–2020

Abstract

Tick-borne encephalitis (TBE) is a growing public health problem with increasing incidence and expanding risk areas. Improved prevention requires better understanding of the spatial distribution and ecological determinants of TBE transmission. However, a TBE risk map at sub-district level is still missing for Germany. We investigated the distribution and geo-spatial characteristics of 567 self-reported places of probable TBE infection (POI) from 359 cases notified in 2018–2020 in the study area of Bavaria and Baden-Wuerttemberg, compared to 41 confirmed TBE foci and 1701 random comparator places. We built an ecological niche model to interpolate TBE risk to the entire study area. POI were distributed heterogeneously at sub-district level, as predicted probabilities varied markedly across regions (range 0–93%). POI were spatially associated with abiotic, biotic, and anthropogenic geo-spatial characteristics, including summer precipitation, population density, and annual frost days. The model performed with 69% sensitivity and 63% specificity at an optimised probability threshold (0.28) and an area under the curve of 0.73. We observed high predictive probabilities in small-scale areas, consistent with the known circulation of the TBE virus in spatially restricted microfoci. Supported by further field work, our findings may help identify new TBE foci. Our fine-grained risk map could supplement targeted prevention in risk areas.

Decoding the Geography of Natural TBEV Microfoci in Germany: A Geostatistical Approach Based on Land-Use Patterns and Climatological Conditions

“…In this context, it should be a matter of debate whether the current risk classification of the RKI, based on notification data, should be revised or complemented by our results, which are derived from vector biological factors/findings. Overall, our data are consistent with findings from a recently published work, which used the self-reported points ( n = 567) of potential infection (POI) and a smaller amount of known microfoci ( n = 41) for analyses and an ecological niche model [ 19 ], exclusively regarding the high-endemic federal states of Bavaria and Baden-Wuerttemberg. To determine the characteristics of the POIs, comparator points/polygons were generated.…”

“…A strength of our study was the fine-grained resolution of 400 × 400 m, which enabled detailed spatial statements. Previous analyses used 10 × 10 km resolutions at a subdistrict level for the illustration of potential POIs [ 19 ]. Furthermore, our findings are based on defined TBEV microfoci with known histories of infection and the repeated confirmation of the virus during the last years, resulting in an in-depth forecasting model of TBEV microfoci.…”

“…The majority of these studies are based on aggregated data using NUTS (Nomenclature of Territorial Units for Statistics) level 3 [ 18 ]. A recently published work from Germany generated a sub-district risk-map for TBE, exclusively for southern Germany, based on 567 probable self-reported places of infection (POI) and 41 confirmed places/foci of infection [ 19 ]. The POI were associated with specific ecological and anthropogenic aspects—the derived information resulted in a 69% sensitivity and 63% specificity [ 19 ].…”

“…A recently published work from Germany generated a sub-district risk-map for TBE, exclusively for southern Germany, based on 567 probable self-reported places of infection (POI) and 41 confirmed places/foci of infection [ 19 ]. The POI were associated with specific ecological and anthropogenic aspects—the derived information resulted in a 69% sensitivity and 63% specificity [ 19 ]. It is known, that TBEV is not homogeneously distributed throughout questing ticks across all locations.…”

Spatiotemporal spread of tick-borne encephalitis in the EU/EEA, 2012 to 2020

“…Finally, we have provided the highest level of geographical detail available (NUTS-3 regions) but acknowledge that the risk is not equally spread throughout these regions. In fact, the distribution of TBEV is generally very focal and patchy, as illustrated in a recent study in Southern Germany [42].…”