Fine-scale heterogeneity and local amplification of West Nile virus in urban environments in Berlin.

Climate change can intensify mosquito-borne disease risks through rising temperatures and more frequent extreme weather events. To mitigate effects of climate change, cities are adopting nature-based solutions, such as urban greening and rainwater management, yet their implications for vector-borne diseases and host community composition remain poorly understood. West Nile virus (WNV), an emerging mosquito-borne human pathogen in Europe, is primarily transmitted between birds and mosquitoes. Using mosquito sampling at five sites within a one-square-kilometre area in Berlin, Germany, we examined how urban land cover, including climate-resilient infrastructure, influences local WNV amplification over two mosquito seasons in 2023 and 2024. We found seasonal WNV infection rates of up to 4.8% in mosquitoes and identified fine-scale heterogeneity in infection risk. Residential areas and cemeteries exhibited the highest minimum infection rates per month (up to 15 and 21, respectively), whereas natural conversation and sponge city sites showed significantly lower rates (up to 4 and 13, respectively). These patterns were not explained by mosquito abundance or species composition but by habitat characteristics and avian host community structure. Our findings reveal that urban land cover shapes WNV infection risk and suggest that incorporating biodiversity restoration into nature-based solutions may serve as strategy for sustainable climate-resilient urban planning.