Viral zoonotic risk is homogenous among taxonomic orders of mammalian and avian reservoir hosts

Abstract

The notion that certain animal groups disproportionately maintain and transmit viruses to humans due to broad-scale differences in ecology, life history, and physiology currently influences global health surveillance and research in disease ecology, virology, and immunology. To directly test whether such "special reservoirs" of zoonoses exist, we used literature searches to construct the largest existing dataset of virus-reservoir relationships, consisting of the avian and mammalian reservoir hosts of 415 RNA and DNA viruses along with their histories of human infection. Reservoir host effects on the propensity of viruses to have been reported as infecting humans were rare and when present were restricted to one or two viral families. The data instead support a largely host-neutral explanation for the distribution of human-infecting viruses across the animal orders studied. After controlling for higher baseline viral richness in mammals versus birds, the observed number of zoonoses per animal order increased as a function of their species richness. Animal orders of established importance as zoonotic reservoirs including bats and rodents were unexceptional, maintaining numbers of zoonoses that closely matched expectations for mammalian groups of their size. Our findings show that variation in the frequency of zoonoses among animal orders can be explained without invoking special ecological or immunological relationships between hosts and viruses, pointing to a need to reconsider current approaches aimed at finding and predicting novel zoonoses.infectious disease | reservoir | surveillance | generalized additive model

COVID-19 and the Curse of Piecemeal Perspectives

“…Closing 50 markets appears frivolous at best ( 23 ); (iii) The focus on so-called high-risk species lacks evidence and defies enforcement. Numerically abundant orders such as rodents and bats harbor more viruses, but the notion of “special viral reservoirs” has recently been revoked ( 24 ). Most pathogens in wildlife remain unidentified, and many spillover events are overlooked ( 19 ).…”

Expanding host specificity and pathogen sharing beyond viruses

“…This fact has warranted various analyses into the factors that shape the zoonotic potential of viruses and their patterns of cross‐species transmission. For example, RNA viruses and those transmitted by arthropod vectors are more likely to infect humans (Olival et al., 2017), and host taxa such as rodents and bats generally harbour more zoonotic viruses by nature of being more speciose than other orders of mammals or birds (Mollentze & Streicker, 2020). Cross‐species transmission of viruses is further structured by seemingly general phylogeographic rules, such that more phylogenetically similar host species and those with greater geographic overlap are more likely to share viruses (Albery, Eskew, Ross, & Olival, 2020).…”

A Potent Postentry Restriction to Primate Lentiviruses in a Yinpterochiropteran Bat

“…The complex issue of whether bats have evolved to be especially convivial viral reservoirs has drawn attention and has been reviewed well elsewhere ( 3 , 7 – 9 ). Some analyses ( 2 , 10 ) but not others ( 11 ) have suggested that, per species, bats host more zoonotic viruses than rodents and other mammalian orders. Bat characteristics that could contribute to disproportionate viral reservoir capacity include abundance; aggregation in large, dense colonies; ability to propagate viruses widely as the only mammals that have achieved flight; extreme longevity relative to size and metabolic rate (many species live longer than 25 years) ( 7 ); and distinctive innate immune system properties ( 12 – 14 ).…”