According to a new study, the novel coronavirus that causes Covid-19 might have started spreading in China as early as October 2019 which was two months prior to the detection of the first case of the disease in the central Chinese city of Wuhan.
Such an estimate was made using methods from conservation science by researchers from Britain’s University of Kent and they concluded that SARS-CoV-2 first emerged from early October to mid-November 2019.
The research paper was published in the PLOS Pathogens journal.
The researchers estimated that November 17, 2019 was the most probable date of the emergence of the novel coronavirus and the virus had probably spread globally by January 2020. The first official Covid-19 case in China was declared to have happened in December 2019 and was most likely linked to the Huanan seafood market of Wuhan.
The researchers have also concluded that a few of the earliest cases of the disease potentially also had no connection with Huanan which means that SARS-CoV-2 was already circulating in China even before it reached the wet market where live animals are sold.
The estimation that the disease could have caused sporadic human infections prior to the Hunan outbreak was acknowledged in a joint study published by China and the World Health Organization at the end of March.
Deleted sequencing data from early Covid-19 cases in China were recovered by Jesse Bloom of the Fred Hutchinson Cancer Research Center in Seattle who published the data in a paper released in preprintform earlier this week.
According to that data, the SARS-CoV-2 as a whole were not adequately represented by samples taken from the Huanan market and those were a variant of a progenitor sequence that must have already been circulating prior to the Wuhan cases and then spread to other parts of China.
In March 2020, the samples used in the study were submitted to the Sequence Read Archive (SRA) but were later deleted on the requests of the Chinese investigators who claimed that the samples would be further updated and then submitted to another archive.
However critics have argued that the requested deletion of the samples was further evidence that efforts of covering up of origins of Covid-19 by Chinese authorities.
“Why would scientists ask international databases to delete key data that informs us about how COVID-19 began in Wuhan?” said Alina Chan, a researcher with Harvard’s Broad Institute, writing on Twitter.
Genomic data was used to show that SARS-CoV-2 binds to human receptors far more easily than other species which suggested that the virus had already adapted to humans at the time of its first official emergence, claimed another study by Australian scientists which was published on Thursday in the Scientific Reports journal.
The study also propagated the possibility of the presence of another yet unidentified animal which had even stronger affinity that acted as an intermediary species. However the study also did not rule out the possibility of the virus having leaked from a lab in China.
“While it is clear early viruses had a high propensity for human receptors, that doesn’t mean they were ‘man-made’,” said Dominic Dwyer, infectious disease expert at Australia’s Westmead Hospital who was part of the WHO team investigating COVID-19 in Wuhan this year.
“Such conclusions remain speculative,” he said.
According to Stuart Turville, associate professor at the Kirby Institute, an Australian medical research organisation who was responding to the University of Kent study, in order to say anything conclusively about the origins of Covid-19, there was need for testing of serum samples.
“Unfortunately with the current pressure of the lab leak hypothesis and the sensitivities in doing this follow-up research in China, it may be some time till we see reports like that,” he said.
(Adapted from NDTV.com)