The composition of host communities is pivotal for pathogen persistence and transmission. We present a community competence index (CCI), based on the Amplification Fraction framework, and applied it to the West Nile virus (WNV) system, and its avian and mosquito hosts, using field data from France, Germany, and Mexico across several land-use types. Our results showed that urban areas exhibited significantly higher AF and CCI values compared to rural and natural habitats. These findings suggest that the lower diversity distinctive of urban communities is associated with higher average community competence, supporting the hypothesis of the dilution effect hypothesis, in which high richness can dilute pathogen transmission. The CCI provides a versatile and integrative tool for estimating pathogen transmission capacity at the community level, complementing existing strategies for the early prevention, surveillance, and risk assessment of zoonotic diseases.