The Ability of SARS-CoV-2 to Transmit to New Hosts Evolved in Bats
In December of 2019, a novel coronavirus was first reported in Wuhan, China. Evolutionary analysis identified the virus as a severe acute respiratory syndrome-related virus (SARS) with many similarities to the first SARS-CoV (Wu et al. 2020). It was subsequently named Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Since then, SARS-CoV-2 has spread around the world, greatly disrupting social and economic interactions. The direct origin of the pandemic is unknown. While it is known that these viruses are found in horseshoe bats, the sudden transmission to human hosts represents decades of evolution (Boni et al. 2020). How exactly did this occur? What extent of evolution is required for a bat virus to transmit to humans? Researchers at MRC-University of Glasgow Centre for Virus Research set out to answer these questions.
The ability to replicate efficiently and spread successfully is something most RNA viruses acquire after switching to the new host species. However, SARS-CoV-2 comes from the family of Sarbecoviruses which already transmit frequently between bat species because of their generalist properties. These viruses have evolved spike proteins to latch onto cells. They then bind to angiotensin-converting enzyme receptors for cell entry. Coincidentally, this allows them to successfully infect non-bat species, including humans, by binding to the human angiotensin-converting enzyme receptors. The researchers hypothesized that because of these prior adaptations that occurred in bats, SARS-CoV-2 did not need additional adaptations to transmit to humans.