The spatial pattern of human exposure to Crimean-Congo haemorrhagic fever virus is not consistent with red deer-based risk predictions

The objective of this study was to evaluate the spatial risk of exposure to Crimean-Congo haemorrhagic fever virus (CCHFV) infection of healthy blood donors in an enzootic region with a predicted risk gradient based on a virus-animal interaction risk model. We designed a cross-sectional study to test if the exposure pattern of the human population to CCHFV spatially matches the predicted risk. We randomly selected 1384 donors from different risk gradients and analyzed their sera searching for CCHFV antibodies. None of the selected blood donors showed exposure to CCHFV. This study shows that exposure risk spatial patterns, as predicted from animal-tick-virus models, does not necessarily match the pattern of human-infected tick interactions leading to CCHFV infection and CCHF cases, at least in a region of predicted moderate infection risk. The findings suggest that future studies should bear the potential drivers of tick-human encounter rates into account to more accurately predict risks.