The novel coronavirus that has claimed the lives of more than 2,400 people did not originate at a seafood market in the central China city of Wuhan as was first thought, according to a new study by a team of Chinese scientists.
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was instead imported from elsewhere, said researchers from Xishuangbanna Tropical Botanical Garden under the Chinese Academy of Sciences and the Chinese Institute for Brain Research.
The team, led by Dr Yu Wenbin, sequenced the genomic data of 93 SARS-CoV-2 samples provided by 12 countries in a bid to track down the source of the infection and understand how it spreads.
What they found was that while the virus had spread rapidly within the Huanan Seafood Wholesale Market in Wuhan, there had also been two major population expansions on Dec 8 and Jan 6.
According to the study, which was published on the institute's website on Thursday, analysis suggested that the coronavirus was introduced from outside the market.
"The crowded market then boosted SARS-CoV-2 circulation and spread it to the whole city in early December 2019," it said.
Earlier reports by Chinese health authorities and the World Health Organisation said that the first known patient showed symptoms on Dec 8, and that most of the subsequent cases had links to the seafood market, which was closed on Jan 1.
The research went on to say that based on the genome data it was possible that the virus began spreading from person to person in early December or even as early as late November.
"The study concerning whether Huanan market is the only birthplace of SARS-CoV-2 is of great significance for finding its source and determining the intermediate host, so as to control the epidemic and prevent it from spreading again," the research team said.
The scientists said also that although China's National Centre for Disease Control and Prevention issued a Level 2 emergency warning about the new coronavirus on Jan 6, the information was not widely shared.
"If the warning had attracted more attention, the number of cases both nationally and globally in mid-to-late January would have been reduced," they said.
Meanwhile, Xiang Nijuan, a researcher at the Chinese Centre for Disease Control and Prevention, said in an interview with state broadcaster CCTV on Saturday that people infected with the new coronavirus were contagious two days before they showed any symptoms.
Therefore anyone who had been in close contact with someone within 48 hours of them being confirmed as infected should put themselves in isolation for 14 days, he said.
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This article was first published in South China Morning Post.