Figure 1.

The three species barriers to zoonotic transmission and the factors that influence the ability of emerging or re-emerging zoonotic pathogens to cause epidemics/pandemics in humans. For a pathogen to be able to establish sustainable transmission chains in humans, all three barriers must be effectively surpassed. Boxes shown in red concern the pathogen and host factors and their interactions that are crucial in determining the relative success of a species jump for an animal virus to humans and which are developed further in this review. Further details are given in the text. Adapted with permission from [19]. Copyright 2022, Revue CONFLUENCE Sciences & Humanités.