FIGURE 1.

Criteria to assess the zoonotic risk of animal viruses to cause epidemics in the human population. The Warren and Sawyer (2023) criteria to assess the potential of an animal virus to enter and to be transmitted in the human population are illustrated on the left side of the diagram. These criteria need an extension to evaluate the potential of such viruses to be transmitted in the human population and to cause significant disease (left side, bottom). The Warren and Sawyer criteria do not specify how candidate animal viral viruses are chosen for investigation. The right side of the figure illustrates a possible flow scheme to identify candidate animal viruses for analysis. After virus isolation, such candidate viruses can be submitted to the modified Warren and Sawyer flow scheme to characterize their pandemic potential. See text for details.