By genetic analysis of HIV, Worobey, Lemey and colleagues from the social sciences "cleared" Gaëtan Dugas, a Canadian air steward, who previously had been identified by name as Patient Zero--the source of the epidemic. Unfortunately Dugas was cleared of his responsibility only after his death. One lesson that researchers drew from this was not to identify patients by name in contexts like this. Full text available from PubMedCentral at this link. Order of authorship in the original publication was Worobey, Watts, McKay...Lemey....

(Thanks to Juan Weiss for this reference and its interpretation.)

Worobey and colleagues showed:

1) The earliest case of an abnormal pneumonia was first reported to the World Health Organization on Dec. 31, 2019.

2) Using basic epidemiology going back to the now iconic plot maps drawn by John Snow in the 19th century, the authors showed with their 21st century maps that nearly all the reported cases in December 2019 to February of 2020, were reported within a circumferential radius around the Wuhan market, which was defined at about a 13 kilometer radius, but with the greatest group of cases within 8.3 kilometers of the market.

3) They determined that a "lineage B" strain was clustered around a 1.12 km. radius around the market and that a "lineage A" strain was identified beyond a 3.2 kilometer radius. On their maps there is a tight clustering of cases contained within an 8.3 km cluster around the market.

4) They showed that 11 infection susceptible animals were observed and documented at the Huanan market in November 2019, with the raccoon dog being perhaps the most salient. The Wuhan market traded and sold each and all of these raccoon dogs.

5) They suggested that the market was a superspreading event which would be lineage specific. Evidence suggests that lineage A and B likely originated at the market, and then spread from this epicenter into the neighborhoods surrounding the market and beyond.

6) China has not reported the early virological studies done on these animals at the market , so the Chinese are the only ones that know which animals tested positive.

7) Based on their data, the authors posited animal to human viral transmission plausibly from infected live animals at the market. They stated  that “there were probably two viral introductions (A and B), and there was an extensive network of wildlife farms in Wester Hubei Province, including hundreds of thousands of raccoon dogs on farms in Enshi Prefecture, which specifically
supplied the Huanan market."

Order of authorship in the original publication: Worobey, Levy... Lemey....

Digital text from science.org at this link.

(Thanks to Juan Weiss for this reference and its interpretation.)

Abstract: "We analyzed the genomic diversity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) early in the coronavirus disease 2019 (COVID-19) pandemic. We show that SARS-CoV-2 genomic diversity before February 2020 likely comprised only two distinct viral lineages, denoted “A” and “B.” Phylodynamic rooting methods, coupled with epidemic simulations, reveal that these lineages were the result of at least two separate cross-species transmission events into humans. The first zoonotic transmission likely involved lineage B viruses around 18 November 2019 (23 October to 8 December), and the separate introduction of lineage A likely occurred within weeks of this event. These findings indicate that it is unlikely that SARS-CoV-2 circulated widely in humans before November 2019 and define the narrow window between when SARS-CoV-2 first jumped into humans and when the first cases of COVID-19 were reported. As with other coronaviruses, SARS-CoV-2 emergence likely resulted from multiple zoonotic events."

Digital text from science.org at this link.

Thanks to Juan Weiss for this reference.