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.

In today's landscape of zoonotic pathogen outbreaks, the dilution effect theory, i.e., the theory that greater biodiversity can help curb pathogen transmission among wildlife, has gained significant attention. However, the positive link between animal diversity and pathogen richness urges us to apply this concept with caution. It is crucial to explore how conservation biology can safeguard human health by preventing the emergence of zoonotic diseases. By investigating the implications of conservation strategies on animal communities and pathogen transmission as well as the adaptive capabilities of pathogens, we propose that biodiversity conservation based on small reserves can effectively reduce pathogen spread in wildlife, provided certain measurable conditions are met. Given the urgent need to tackle both zoonoses disease emergence and biodiversity loss, these interventions should be prioritized and implemented without delay.

Concerns about the prospect of a global pandemic have been triggered many times during the last two decades. These have been realized through the current COVID-19 pandemic, due to a new coronavirus SARS-CoV2, which has impacted almost every country on Earth. Here, we show how considering the pandemic through the lenses of the evolutionary ecology of pathogens can help better understand the root causes and devise solutions to prevent the emergence of future pandemics. We call for better integration of these approaches into transdisciplinary research and invite scientists working on the evolutionary ecology of pathogens to contribute to a more “solution-oriented” agenda with practical applications, emulating similar movements in the field of economics in recent decades.

Despite important implications for biological conservation and public health, the potential generality of a prophylactic effect of biodiversity on zoonotic pathogen transmission (e.g., dilution effect) remains hotly debated, potentially because existing studies focus on different kinds of analyses as well as different spatial scales. Here, we test if changing the spatial scale of analysis can affect the detection of a relationship between hantavirus infection prevalence and rodent species richness throughout the World. We found that these relationships are always negative, whatever the spatial scale. Nevertheless, the dilution effect magnitude decreases if larger spatial scales are considered. These results, which remain consistent for all regions, highlight that the dilution effect should be a general phenomenon for hantaviruses, but that its detection can be hampered by the spatial scale considered. Finally, we discuss the mechanisms that can hinder the observation of a dilution effect and the necessity to consider other host-pathogen systems.