Since the revival of the lab-leak theory will once again enliven conspiracy theorists, it’s worth being reminded why it’s wildly implausible that SARS-CoV-2 was created in the Wuhan Institute of Virology as a biological weapon. (Also keep in mind that the possibility that the virus accidentally leaked from the lab does not contradict the still widely held view that it originated in the wild.) Last July, Ruby Prosser Scully wrote:

[C]reating this virus in a lab and knowing that it could be a pandemic-inducing pathogen seems to be more in the realms of science fiction than present-day science.

If you were a scientist designing such a virus, the first thing you would need is an existing template, explains Dr [Megan] Steain [lecturer in infectious diseases & immunology at the University of Sydney]. “You don’t just assemble it from nothing in the lab.”

We would expect engineers to choose a virus that already causes disease, such as the first SARS-coronavirus, as the backbone for the new virus, she says.

“And if you were to do that, you can’t make sweeping changes across the whole genome, you would generally just mutate in specific regions as you go.”

The end result would be something that looks a lot like the virus backbone that you started with, but has particular mutations in a particular region.

“Whereas when we look at the genome to this virus, it doesn’t look like it’s come from any of those existing backbones,” Dr Steain says.

Instead, the virus with the most genetic similarities, RaTG13, is unlikely to be able to efficiently infect human cells. This would make it an unlikely candidate to base your weapon on if you were a scientist aiming to make a deadly and very infectious virus. [Continue reading…]