The virus that causes COVID-19 may have started spreading in China as early as October 2019, two months before the first case was found in the central city of Wuhan, according to a new study published on Friday (June 25).
According to a paper published in the journal Public Library of Science: Pathogens (PLOS Pathogens), researchers at the University of Kent in the United Kingdom used a conservation science approach to estimate that SARS-CoV-2 first emerged in early October to mid-November 2019.
Reuters reports that the University of Kent researchers estimate that the most likely date for the virus to emerge is Nov. 17, 2019, and that it could have spread globally by January 2020.
The first officially released case of 2019 coronavirus disease (COVID-19) in China occurred in December 2019. The case was thought to be associated with the South China Seafood Market in Wuhan.
However, some early cases had no known association with South China. This means that the virus causing the disease, Sars-Coronavirus-2 (SARS-CoV-2), was spreading before it entered the South China seafood market.
A joint study by China and the World Health Organization published in late March this year acknowledged that COVID-19 may have preceded the Wuhan outbreak with sporadic human infections.
In a paper released as a preprint this week, Jesse Bloom of the Fred Hutchinson Cancer Research Center in Seattle recovered sequencing data from deleted early COVID-19 cases in China, Reuters reported.
The data show that virus samples collected from the South China market do not fully represent SARS-CoV-2, a variant of an earlier transmitted parental sequence that has spread to other parts of China.
Reuters reports that the NIH confirmed that the samples used in the study were submitted to the Sequence Read Archive (SRA) in March 2020 and were later removed at the request of Chinese investigators. They said they would update the samples and submit them to another dossier.
Critics say the removal of the samples is further evidence that China is trying to cover up the origin of COVID-19.
Alina Chan, a researcher at Harvard University’s Broad Institute, tweeted, “Why would scientists ask an international database to remove critical data that tells us how COVID-19 started in Wuhan?”
Another study by Australian scientists, published Thursday in the journal Scientific Reports, used genomic data to show that SARS-CoV-2 binds more readily to human receptors than other species, suggesting that it was adapted to humans when it first appeared.
The study says there may be another unidentified animal with a stronger affinity as an intermediate species, but the hypothesis that it was leaked from a laboratory cannot be ruled out.
Dominic Dwyer, an infectious disease specialist at Westmead Hospital in Australia, told Reuters, “While it’s clear that the early viruses had a high affinity for human receptors, that doesn’t mean they were ‘artificial ‘”
Dwyer said, “Such a conclusion remains speculative.”
Stuart Turville, an associate professor at the Kirby Institute, an Australian medical research institute, was quoted in the Reuters report as saying that tests on serum samples are still needed to make a stronger case for the origin of COVID-19.
Turville said, “Unfortunately, given the current pressure on the laboratory leak hypothesis and the sensitivity of a follow-up study on this in China, we may have to wait a while before we see a report like that.”