SHANGHAI, June 25 (Reuters) – The virus causing COVID-19 could have spread in China as early as October 2019, two months before the first case was identified in downtown Wuhan, a new study showed on Friday.
Researchers at the UK’s University of Kent used conservation science methods to estimate that SARS-CoV-2 first appeared from early October to mid-November 2019, according to a paper published in the journal PLOS Pathogens.
The most likely date for the virus to appear was November 17, 2019, and it had likely already spread worldwide by January 2020, they estimated.
China’s first official COVID-19 case occurred in December 2019 and was related to the Huanan seafood market in Wuhan.
However, some early cases had no known association with Huanan, suggesting that SARS-CoV-2 was already in circulation before it hit the market.
A joint study published by China and the World Health Organization in late March confirmed that there may have been sporadic infections in humans prior to the Wuhan outbreak.
In an article published in preprint form this week, Jesse Bloom of the Fred Hutchinson Cancer Research Center in Seattle restored deleted sequencing data from early COVID-19 cases in China.
The data showed that samples from the Huanan market were “not representative” of SARS-CoV-2 overall and were a variant of a previously circulating precursor sequence that spread to other parts of China.
The US National Institutes of Health confirmed to Reuters that the samples used in the study were submitted to the Sequence Read Archive (SRA) in March 2020 and later deleted at the request of Chinese investigators, who said they were updated and sent to another archive would be transmitted.
Critics said the removal is further evidence that China is trying to cover up the origins of COVID-19.
“Why should scientists ask international databases to delete key pieces of information that tell us how COVID-19 began in Wuhan?” Alina Chan, a researcher at Harvard’s Broad Institute, said on Twitter.
Another study by Australian scientists, published Thursday in the journal Scientific Reports, used genomic data to show that SARS-CoV-2 binds to human receptors much more easily than other species, suggesting that it was present when it first appeared was adapted to the people.
It is possible that there might be another unidentified animal with even stronger affinity that served as an intermediate species, but the hypothesis that it escaped the laboratory could not be ruled out.
“While it’s clear that early viruses had a high propensity for human receptors, that doesn’t mean they were ‘man-made,'” said Dominic Dwyer, an infectious disease expert at Westmead Hospital, Australia who was part of the WHO team , the COVID-19 in Wuhan this year.
“Such conclusions remain speculative,” he said.
Serum samples have yet to be tested to further establish the origins of COVID-19, said Stuart Turville, associate professor at the Kirby Institute, an Australian medical research organization that responded to the University of Kent study.
“Unfortunately, with the current pressure of the laboratory leak hypothesis and the sensitivity of doing this follow-up research in China, it may be some time before we see such reports,” he said.
Reporting by David Stanway; Editing by Raju Gopalakrishnan
Our standards: The Thomson Reuters Trust Principles.