Fig. 1.

Alternative conceptual models linking host biodiversity to zoonotic emergence in humans. (A) Total host diversity: In this model, the overall diversity of hosts leads to a pool of pathogens, any one of which could jump to humans. Research assuming this model typically involves comparisons of large geographic areas with innate variation in biodiversity (e.g., along latitudinal gradients or between countries). (B) Zoonotic host diversity: In this model, some species are more likely to host zoonotic pathogens, and it is the diversity of these zoonotic hosts that is most important in determining the risk of zoonotic emergence. Research using the zoonotic host diversity model typically focuses on the distribution or characteristics of a particular taxon (e.g., bats or primates). (C) Zoonotic host diversity and abundance: In this model, the diversity and the abundance of zoonotic hosts determine the risk of zoonotic emergence. Research using this model typically focuses on the effects of changes in natural biodiversity (e.g., through human impacts, on zoonotic pathogens). Modified from an illustration in Ostfeld and Keesing (7).