Origin and spread: On the source of SARS-CoV-2


By concluding that a virus leak from a laboratory in China’s Wuhan, where the SARS-CoV-2 virus first emerged, is “extremely unlikely” and did not require further study, a 17-member WHO team and its Chinese counterparts have put to rest conspiracy theories that emerged early during the pandemic. While many scientists had dismissed the lab-origin theory, in mid-February 2020, a group of 27 prominent scientists from outside China  “strongly condemned conspiracy theories” in a letter published in The Lancet. The group said scientists who had analysed virus genome sequence data shared by China and multiple countries could “overwhelmingly conclude” that SARS-CoV-2, like emerging pathogens, had originated in wildlife. Even a year since the letter and after nearly half-a-million genome submissions to a public database, scientists have not found any sign of direct human influence. The WHO team’s investigation now strongly suggests virus origin to a natural reservoir in bats, but unlikely to have been in Wuhan, which is miles from any natural bat habitat. The virus jumping directly from bats to humans is highly unlikely and initial investigation too suggests the role of an intermediary host species. The team has not been able to confirm the intermediary host.

While early data suggest that the virus could have been circulating in Wuhan for weeks before it was identified in the Chinese city, it asserts that there is no evidence of large outbreaks in Wuhan prior to December 2019. Chinese media reported in early 2020 based on unpublished government data of a Hubei resident infected with the novel virus in mid-November. Also, in a report in The New England Journal of Medicine, scientists from the China CDC  found evidence of human-to-human transmission as early as mid-December 2019, which again suggests virus circulation weeks before it was identified in Wuhan. China officially confirmed human-to-human transmission only in mid-January. While the possibility of transmission via frozen food, a theory embraced by Chinese officials, has not been ruled out, the possibility of such a route appears unlikely as instances of live viruses on packaging have been “rare and isolated”. The WHO visit is just the beginning of a long endeavour to uncover the origin of the virus. It will succeed only when scientific investigation is allowed to follow its course without being politicised. As in the case of the SARS outbreak in the 2000s, China again failed to be truly transparent  during the SARS-CoV-2 outbreak. It can partially undo the damage done by now being more open and cooperative so that future outbreaks of related coronaviruses can be identified and contained early, if not prevented.

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