A study on the Genesis of Covid ( coronavirs SARS-CoV-2) reveals detailed explanation on the emergence of this virus. The paper released Wednesday ii biorxiv ahead of peer-review, and is being prepared for submission to a journal for publication, one of the authors said. It gives a detailed explanation for SARS-CoV-2’s genetic signatures, early epidemiology and research undertaken at the Wuhan Institute of Virology.
The before-outbreak evolutionary history of SARS-CoV-2 is enigmatic because it shares only ~96% genomic similarity with RaTG13, the closest relative so far found in wild animals (horseshoe bats). Since mutations on single-stranded viral RNA are heavily shaped by host factors, the viral mutation signatures can in turn inform the host.
By comparing publically available viral genomes we here inferred the mutations SARS-CoV-2 accumulated before the outbreak and after the split from RaTG13. We found the mutation spectrum of SARS-CoV-2, which measures the relative rates of 12 mutation types, is 99.9% identical to that of RaTG13. It is also similar to that of two other bat coronaviruses but distinct from that evolved in non-bat hosts.
Debate about Covid’s emergence has coalesced around two competing ideas: a laboratory escape or a spillover from animals. The authors, who also include Nobel Prize winner Peter Doherty and Wellcome Trust Director Jeremy Farrar, said there is no evidence that SARS-CoV-2 has a laboratory origin, and the suspicion stems from the coincidence that the pandemic virus was first detected in a city that houses the institute’s maximum biosafety lab that studies coronaviruses and deadly diseases, such as Ebola.
The lab accident theory “cannot be entirely dismissed,” but it’s very unlikely, the authors said, compared with “the numerous and repeated human-animal contacts that occur routinely in the wildlife trade.”
Based on epidemiological data, the Huanan wholesale seafood and produce market in Wuhan was an early epicenter of SARS-CoV-2 infections, the researcher said. Two of the three earliest documented Covid-19 cases were directly linked to the market that sold live, wild animals, as were 28% of all cases reported in December 2019. Overall, 55% of cases during that month had an exposure to either the Huanan or another market in Wuhan, with these cases more prevalent in the first half of that month.
The pandemic virus evolved in a host environment “highly similar, if not identical,” to a bat coronavirus that’s considered the closest match SARS-CoV-2, researchers at Sun Yat-Sen University and Guangzhou University said. Their research, released July 1 on a preprint server, found it would be difficult to duplicate SARS-CoV-2 in cell culture under laboratory conditions.
The study further states, the debate on the natural or unnatural origin of SARS-CoV-2, the causative virus of COVID-19, has existed since the beginning of the outbreak and surged lately3,4. One of the main reasons is that RaTG13, the closest relative so far found (in horseshoe bats Rhinolophus affinis), has only ~96% nucleotide similarities to SARS-CoV-2 (with ~1,200 nucleotide differences). The situation is distinct from the two previous coronavirus outbreaks happened this century (SARS at 2003 and MERS at 2012); in both cases, a closely related virus with over 99% nucleotide similarities to the causative virus was found in wild animals shortly after the start of each outbreak.
Bloomberg, quoting authors, reported that the lab accident theory cannot be entirely dismissed, but it’s very unlikely compared with the numerous and repeated human-animal contacts that occur routinely in the wildlife trade.
