US National Library of Medicine National Institutes of Health：

The fact that severe acute respiratory syndrome coronavirus 2 derived from bat coronaviruses highlights inherent issues of the way we interact with the environment. Talha Burki reports.

Researchers examining coronaviruses and bats are used to working with large numbers. A 2017 study of 12 333 bats from Latin America, Africa, and Asia found that almost 9% carried at least one of 91 distinct coronaviruses. The authors estimated that there are at least 3200 coronaviruses that infect bats.

A paper published in July, 2020, traced the origins of SARS-CoV-2. The researchers concluded that it came from a virus with relatively generalist properties circulating in horseshoe bats.

The picture becomes even more complicated when we start to consider which bat viruses are likely to pose a threat to human beings. “Going after bats will only give you partial information—the viruses you are looking at may or may not get the additional mutations they need to be transmissible among humans”, explains Stanley Perlman, professor of microbiology and immunology at the University of Iowa, IA, USA. “There has almost always been an intermediary involved, and without knowing what that is and what changes the virus would have to undergo, it is very hard to make any kind of predictions.”

“Everything points to a bat sarbecovirus reservoir; we are very confident about this”, said David Robertson, head of bioinformatics at the Medical Research Council–University of Glasgow Centre for Virus Research, Scotland, UK, and co-author of the paper. The evolutionary analysis suggested that the lineage from which SARS-CoV-2 emerged has been present in bats for several decades.

Still, there is one theory that can be dismissed. From the earliest days of the pandemic, there has been speculation that the new virus had escaped, or even been deliberately released, from the Wuhan Institute of Virology. At a White House press conference on May 1, 2020, US President Donald Trump declined to assert that SARS-CoV-2 had occurred naturally. When asked what gave him a “high degree of confidence that this [virus] originated from the Wuhan Institute of Virology”, Trump replied “I can't tell you that. I'm not allowed to tell you that.”