Present estimates suggest there are over one million virus species found in mammals alone, with roughly half a million posing a possible threat to human health. Although previous estimates assume linear scaling between host and virus diversity, we show that ecological network theory predicts a nonlinear relationship, produced by broad patterns of plasticity in host-virus associations. In light of this, we re-estimate global viral diversity, using the most comprehensive available dataset of mammal-virus associations. To account for host sharing, we fit a power law scaling relationship for host-virus species interaction networks, adapting a method previously used to estimate helminth species richness. We show how our new R package, codependent, automates this process and can be used to explore host-parasite scaling relationships.
Results/Conclusions
We estimate that there are approximately 40,000 virus species in mammals, a reduction of two orders of magnitude from current projections of viral diversity. Of those, we expect roughly 10,000 viruses to harbor zoonotic potential, the vast majority being RNA viruses. We expect that the increasing availability of host-virus association data will improve the precision of these estimates, and their utility in the sampling and surveillance of pathogens with pandemic potential. More broadly, we suggest host sharing should be widely included in macroecological approaches to estimating biodiversity, and discuss how our approach to estimating affiliate species richness can be used for other applications in disease ecology and other fields.