Fig. 2.

Relative importance of five major mammalian Orders as hosts of zoonotic viruses based on different metrics. (A) Mean number of viruses per host for all species in the Order. (B) Mean number of viruses per host for species that host at least one virus. (C) Proportion of all species that host at least one virus. (D) Total number of species in the Order that host at least one virus. The variety of metrics used in different studies is a source of confusion in competing claims about taxonomic importance. Plotted from data made available in the supplemental material from Johnson et al. (21); see caveats about these and similar data in SI Appendix.