Understanding the influence of host diversity on infectious disease is a key-debate due to the occurrence of zoonotic diseases in wildlife. Very rare studies focused on the impact of biological diversity upon the circulation of pathogenic agents even if some investigations started to address these pitfalls. They underlined that host biodiversity can play a protective role in human health. But all these studies have not yet focused on the effect of community structure and composition despite its potential role. Here, in both using theory and data, we show what can be the impact of community structure and composition on disease dynamics. First, we study the impact of community composition on disease transmission by using empirical laws coupling local host population abundance and species richness. Second, we study how the community dynamics, modeled by different population dynamics and interactions, can impact on disease dynamics by altering the demography of host species. We then study the impact of reservoir community structure upon density-dependent diseases. We compare these results with avian flu and Puumala virus data. For frequency-dependent diseases, e.g. vector-borne diseases, we analyze the impact of both vector and reservoir community structure. We compare our results with the Lyme disease case for the influence of reservoir community, and with West Nile Fever for the synergistic influence of vector and reservoir communities. In the current context of disease emergence, the understanding of infectious disease dynamics within complex host species communities will be a crucial key for human health.