Can Animals Be Infected with SARS-CoV-2?

Overview of Global Infections

The emergence of the novel SARS-CoV-2 virus has resulted in over 25 million global infections, highlighting its rapid spread among humans. In recent months, there have been sporadic reports indicating that certain animals have also contracted the coronavirus. This raises important questions about the potential for the disease to spread further and whether animals might serve as reservoirs for the virus after human transmission has been curtailed.

Research on Animal Hosts

A recent study published in the Proceedings of the National Academy of Sciences of the United States of America aims to identify which animals are likely to serve as suitable hosts for SARS-CoV-2. The researchers focused on the angiotensin-converting enzyme (ACE2), which acts as a target for the virus’s spike protein, facilitating its entry into host cells. The study delves into the binding characteristics of the virus to ACE2 and the specific regions involved in this process.

ACE2 in Mammals

ACE2 is a highly conserved enzyme across mammalian species, suggesting that SARS-CoV-2 could potentially infect a wide range of mammalian hosts. The study examined the ACE2 sequences in 410 vertebrate species, primarily focusing on 252 mammals, as well as birds, fish, reptiles, and amphibians. Specifically, researchers analyzed a 25-amino-acid segment of ACE2, believed to be critical for the virus’s binding.

Classification of Species Risk

The species were categorized based on the similarity of their ACE2 sequence to that of humans. Animals with 23 or more matching amino acids were classified as “very high” risk. Notably, the 18 species deemed most susceptible to SARS-CoV-2 were primarily primates. Other species at risk included certain dolphins, whales, deer, and rodents, while domesticated animals like cats, cattle, and sheep received a medium risk classification.

Structural Variations in ACE2

The researchers also investigated variations in the structural arrangement of the ACE2 binding site. While significant structural variation was rare among humans, animal ACE2 showed mutations that might enhance the binding affinity for SARS-CoV-2. These mutations appear to be subject to positive selection, indicating a potential evolutionary response to the virus.

Future Research Directions

This study emphasizes the need for further research to better understand how mutations in ACE2 affect the binding of SARS-CoV-2. Such insights would refine the predictive capabilities of existing models. Overall, the findings provide valuable information regarding which animals might be most vulnerable to coronavirus infection and highlight potential intermediate species that could have facilitated the initial transmission from bats to humans.

Reference

Damas J, Hughes GM, Keough KC, Painter CA, Persky NS, Corbo M, et al. Broad host range of SARS-CoV-2 predicted by comparative and structural analysis of ACE2 in vertebrates. Proceedings of the National Academy of Sciences. 2020:202010146.