A thread about the plausible date for the host jump of SARS-CoV-2 into humans. A lot has been published about this, but not all the claims are robust. Below, I'm listing the evidence I personally find believable.
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The first case reported in China dates back to 17 November, from a Hubei Province (Wuhan) resident aged 55 (this case was never officially confirmed, but also never denied)
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scmp.com
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scmp.com
The first reported case from Europe is a 42 year-old man with no known link to China or any recent history of international travel, presenting in a French hospital on 27 December 2019.
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ncbi.nlm.nih.gov
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ncbi.nlm.nih.gov
There have been multiple papers reporting positive serological results for SARS-CoV-2 as early as summer 2019. False positive are common in serological surveys and to me the earliest plausible evidence is from Northern Italy from mid December 2019 on.
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Phylogenetic reconstructions of the earliest common ancestor tend to point to October-Dember 2019. We estimated the jump of SARS-CoV-2 into humans to ~24 November 2019 (95% CI: 6 October 2019 – 11 December 2019).
sciencedirect.com
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sciencedirect.com
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This estimate assumes that a single lineage of SARS-CoV-2 jumped into humans.
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Also this estimate is probable slightly biased towards a more recent emergence. The earliest cases were sampled retrospectively, but we used 'raw' collection dates. Taking this delay into account might push back the point estimate by ~1-2 weeks.
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Under the assumption of multiple host jumps into humans, Pekar et al. obtained an estimate around 18 November 2019 (23 October to 8 December), largely in line with the former but with a narrower confidence interval.
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science.org
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science.org
The evidence listed in this thread is based on three independent approaches (direct, serology and phylogenetics), but is highly consistent and points to a host jump of SARS-CoV-2 into humans around November 2019.
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The evidence also fits a scenario of an initial emergence in China, followed by rapid transmission to Europe, with Northern Italy having acted as the epicentre of the spread to the rest of the world.
sciencedirect.com
sciencedirect.com
There's nothing new in this thread but I felt it may be worthwhile summarising the available evidence again, as it provides a framework for discussions evaluating the significance of WIV personnel being among the earliest known cases, assuming this were to be confirmed.
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