Tag Archives: disease risk

The More the Merrier

Viral zoonotic risk is homogenous among taxonomic orders of mammalian and avian reservoir hosts (2020) Mollentze & Streicker, PNAS. https://doi.org/10.1073/pnas.1919176117

Image Credit: Tom Spinker, CC BY-NC-ND 2.0

The Crux

Diseases that jump from other animals to humans, or zoonotic diseases (see Did You Know?) have become something that all of us are now very familiar with. COVID-19 is one such disease, and the impact it has had on the world as a whole is all the evidence that anyone could ever need for understanding why it is important to know where these diseases come from. Classically, specific groups of animals have been thought to act as reservoirs for the viruses that cause these diseases. Take rabies, for example. This is the disease that results in rabid animals, but you may not know that bats act as a reservoir for rabies, meaning that the rabies virus survives within bat populations and can be spread by them.

This is known as the “special reservoir hypothesis”, and it posits that there are certain traits associated with these reservoir species and/or their ecology that make them more likely to act as reservoirs for these viruses. In contrast, it could be that all animal species are equally likely to act as a reservoir for zoonotic viruses, and the risk of virus transmission is instead due to how many host species are within a given group of animal hosts. All this means is that you expect to find more diverse groups of animals hosting a more diverse group of viruses. This is known as the “reservoir richness hypothesis”.

In order to better manage zoonotic disease emergence and even predict where it is likely to occur in the future, it is important to understand if there are indeed special reservoirs among animal hosts, or if disease emergence is instead a consequence of host species richness. Today’s authors utilized data on zoonotic viruses and host species to understand this relationship.

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