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

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. “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.

“The generalist property of the virus means an intermediate host is not required for any evolutionary change”, said Robertson. “As the virus has been around for decades it may have emerged in another host and this could be the missing intermediate species but we are inferring that this would only facilitate transmission.” The fact that SARS-CoV-2 was first detected in Wuhan, China, far from where the horseshoe bat is found, hints at the presence of an intermediary.

Some have posited that the pangolin could be this missing link. Pangolins have reportedly fallen sick as a result of coronavirus infection, which would mean they are not a natural reservoir. But that leaves the possibility that the pangolin is facilitating transmission to humans. SARS-CoV-2 can jump to other animals such ferrets and cats. “The virus would not need to evolve in the pangolin, it would just need to be brought into contact with humans”, explains Robertson. And it is still too soon to rule out direct bat–human transmission.

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.”

“If the virus had been human-made, that would show in its genome”, counters Robertson. “Besides, if you were going to create a coronavirus that can be transmitted by humans, you would almost certainly start with the first SARS virus. SARS-CoV-2 is like nothing we have seen before. It really is highly unlikely that someone created it; it is not put together from pieces we know about.” SARS-CoV-2 is closely related to other beta coronaviruses such as RaTG13, a bat virus that the Wuhan Institute of Virology has been working on. But it only shares 96% of its genome sequence with RaTG13, which makes them roughly as similar as human beings and chimpanzees, and points to a common ancestor rather than one springing from the other.