Predicting the risk of tick-borne diseases.

This brief review focuses on the value of predictive risk mapping and the question of how to test predictions of the spatial and temporal variation in risk of tick-borne diseases, specifically as caused by tick-borne encephalitis virus (TBEv). Predictions of the present distribution of TBEv, driven by satellite data, match the mapped records of TBE cases with 90% accuracy in the Baltic region and 81% accuracy in central Europe. Many of the apparently false predictions of TBE presence coincide with recent records of new or reactivated foci, and highlight regions for active surveillance. Predictions of the changes in TBEv distribution under the influence of climate change suggest that TBEv may be driven into increasingly high latitude and high altitude regions, until by the 2080s it is confined to parts of Scandinavia. This is consistent with the fact that enzootic TBEv cycles are inherently fragile and depend for their existence on specific seasonal temperature profiles and moisture conditions, which may be disrupted by climate change. Changes in the incidence of TBE in many countries since the 1990s are also consistent with these predictions, although there is evidence that local non-biological factors also play an important role in determining the incidence of disease.