The novel coronavirus behind the COVID-19 pandemic may have jumped from its original animal host into humans as early as October, according to the latest analysis of the changing viral genome.
Scientists analysing the genetic trees of 7,666 SARS-CoV-2 genomes collected from around the world estimated a common ancestor to the circulating COVID virus strains as having most likely appeared in China at some point between Oct. 6 and Dec. 11, 2019.
“The genomic diversity of the global SARS-CoV-2 population being recapitulated in multiple countries points to extensive worldwide transmission of COVID-19, likely from extremely early on in the pandemic,” they write in a paper just published in the peer-reviewed journal Infection, Genetics and Evolution.
This suggests that the virus was probably infecting people in multiple countries weeks or even months before the “official” outbreak began in January 2020 in Wuhan, China.
“All these ideas about trying to find a Patient Zero are pointless because there are so many patient zeros,” genetics researcher Francois Balloux of the University College London Genetics Institute told CNN. “It has been introduced and introduced and introduced in almost all countries.”
However, despite this evidence of the virus already circulating globally much earlier than previously suspected, the scientists squashed the hopeful notion that sufficient numbers of people might already have been exposed to the virus to build up substantial herd immunity around the world.
“This rules out any scenario that assumes SARS-CoV-2 may have been in circulation long before it was identified, and hence have already infected large proportions of the population,” the scientists wrote in their paper, entitled “Emergence of genomic diversity and recurrent mutations in SARS-CoV-2.”
The latest analysis provides no evidence to support recent conspiracy theories asserting that the COVID-19 virus was deliberately created or released, intentionally or otherwise, from a lab. The authors reference earlier genetic analysis making clear that SARS-CoV-2 has natural origins, most likely having jumped into humans originally from bats.
SARS-CoV-2 shares 96 percent of its genome with a horseshoe bat virus called BatCoV RaTG13, which researchers say shows “no evidence of recombination events.” An intermediate animal host connecting this bat virus to human COVID has still not been definitively identified, but is thought to have been pangolins — an endangered animal illegally traded in Asian wildlife markets and also widely used in non-scientific Chinese medicine.
Dr. Anthony Fauci, director of the United States National Institute of Allergies and Infectious Diseases, has also spoken out strongly against ideas of deliberate or even accidental release from a Chinese lab. “Everything about the stepwise evolution over time strongly indicates that [this virus] evolved in nature and then jumped species,” Fauci told National Geographic.
There is some good news from this latest genomic analysis because it shows only a limited rate of mutations among the multiple strains of SARS-CoV-2, which still have enough of their genes and proteins in common to mean that any vaccine or treatment drug should have long-term efficacy.
The study also helps identify the parts of the SARS-CoV-2 genome which are “conserved” — meaning they stay the same despite other genetic variations — helping vaccine researchers better identify targets for their differing approaches. The researchers write that “it is important to stress that there is no evidence for the evolution of distinct phenotypes in SARS-CoV-2 at this stage.”
According to the World Health Organization, there are now more than 100 COVID-19 candidate vaccines in development around the world.