Vegetated urban spaces increase Aedes albopictus survival and the risk of Dengue and Chikungunya Transmission: a field and modelling study in Montpellier, France

IntroductionBy 2025, Aedes albopictus had spread across France, leading to a rise in indigenous arboviral cases since 2021. While urban greening is promoted for its health and climate benefits, its potential adverse effects on arboviral risk remain understudied. Urban green spaces may enhance mosquito habitats and human-vector contact. MethodsThis study investigates the variation in Aedes albopictus longevity across months and urban environments in Montpellier, a green Mediterranean city, and its impact on the theoretical basic reproductive number (R0) for Chikungunya, Dengue, and Zika viruses. From May to October 2023, female mosquitoes were sampled monthly using CO2 traps in three urban environments: urban parks, impervious areas, and residential areas composed of houses with gardens. Daily mosquito survival was estimated from parity rate measurements, and the associated environmental determinants were analysed. Modelled predictions, crude field estimates of vector density and parity rates, and microclimatic data were used to parameterize and feed R0 models. For each environment (or sampling area), 1000 monthly R0 simulations were run, followed by sensitivity analyses. Results/DiscussionThe highest mean daily survival (0.917) was observed in residential areas, compared to parks (0.887) and impervious areas (0.873). A daily average exposure of 10% of possible bites induces potential transmission risks for CHIKV and DENV. R0 varied by environment and month, with higher values in residential areas and with greater variability in impervious areas. Parity rate emerged as the main driver of R0 variability. These results highlight the value of fine-scale field data for arboviral risk assessment.