A new paper is suggesting dogs played a role in the origin of SARS-CoV-2.

Doubtful. I suspect this will be like the snake-origin story… lots of initial press but ultimately not much support. (The snake paper was largely debunked within about 24 hours.)

The current study, released a few minutes ago by the journal Microbial Biology and Evolution (Xia et al. 2020), postulates that dogs played a role as a bridging host, with SARS-CoV-2 developing in the dog’s gut after eating bats. Some of the genomics are beyond my skill set, but it looks very dodgy.

The researcher looked at one protein, zinc finger antiviral protein (ZAP), that binds specifically to CpG dinucleotides in viruses. A host uses the ZAP protein to inhibit viral replication and eliminate a given virus. Lower CpG levels in viruses might make it harder for the virus to be eliminated by the host, making decreasing CpG levels a potential protective mechanism that could evolve in RNA viruses.  This study (which strangely has only a single author… something that is exceedingly rare) reported extremely low  CpG in the virus that causes COVID-19. When the author looked at different viral genomes for comparison,  one canine coronavirus strain also had a very low CpG level, similar to that observed in SARS-CoV-2.

This was taken to suggest that  “canine tissue infected by the canine coronavirus may provide a cellular environment strongly selecting against CpG.” So the author proposed that the ancestor of SARS-CoV-2 “infected the intestine of a mammalian species (e.g., canids or human ingesting bat meat)” and that the strong selection pressure against CpG resulted in rapid evolution the virus, and that “the licking of anal regions in canids during mating and other circumstances facilitate viral transmission from the digestive system to the respiratory system.” The author then concluded that these genomic changes allowed the virus to “to evade human ZAP-mediated immune response and became a severe human pathogen.

Wow… that’s not just a leap, it’s a… (well, I can’t come up with a good term for it, but it’s way more than a leap).

I can’t see this holding up to much scrutiny. Let’s hope it doesn’t cause much damage and freak people out in the interim.