First Covid-19 case could have emerged in China in October 2019: Study

SHANGHAI • The virus that causes Covid-19 could have started spreading in China as early as October 2019, two months before the first case was identified in Wuhan, a new study showed yesterday.

Researchers from Britain's University of Kent used methods from conservation science to estimate that Sars-CoV-2 first appeared from early October to mid-November in 2019, according to a paper in the PLOS Pathogens journal.

The most likely date for the coronavirus' emergence was Nov 17, 2019, and it had probably already spread globally by January last year, they estimated.

China's first official Covid-19 case, in December 2019, was linked to Wuhan's Huanan seafood market. But some cases had no known link with Huanan, implying that the virus was already circulating before it reached the market.

A joint study published by China and the World Health Organisation (WHO) in March this year acknowledged that there could have been human infections before the Wuhan outbreak.

In a paper released this week, virus expert Jesse Bloom of the Fred Hutchinson Cancer Research Centre in Seattle recovered deleted sequencing data from early Covid-19 cases in China.

The data showed that Huanan samples were "not representative" of Sars-CoV-2 as a whole and were a variant of a progenitor sequence circulating earlier, which spread to other parts of China.

The United States National Institutes of Health confirmed that the samples were submitted to the Sequence Read Archive in March last year and later deleted at the request of Chinese investigators, who said they would be updated and submitted to another archive.

Critics said the deletion was further evidence that China was trying to cover up the virus' origins.

"Why would scientists ask international databases to delete key data that informs us about how Covid-19 began in Wuhan?" asked Dr Alina Chan, a researcher with Harvard's Broad Institute.

Another study, published in the Scientific Reports journal, used genomic data to show that the virus binds to human receptors far more easily than other species, suggesting it was already adapted to humans when it emerged.

It said it was possible there was another unidentified animal with even stronger affinity that served as an intermediary species, but the hypothesis that the virus leaked from the lab could not be ruled out.

"While it is clear early viruses had a high propensity for human receptors, that doesn't mean they were 'man-made'," said Dr Dominic Dwyer, an Australian infectious diseases expert who was part of the WHO team investigating Covid-19 in Wuhan this year. "Such conclusions remain speculative." REUTERS