[1][2] The letter, published in the journal Nature Medicine on 17 March 2020, was written by a group of virologists including Kristian G. Andersen, Andrew Rambaut, W. Ian Lipkin, Edward C. Holmes and Robert F. Garry.
Different versions of the lab origin hypothesis present different scenarios in which a bat-borne progenitor of SARS-CoV-2 may have spilled over to humans, including a laboratory-acquired infection of a natural or engineered virus.
In an earlier email obtained by public records request, Proximal Origins lead author Kristian G. Andersen said they were focused on dispelling these rumors, saying "the main crackpot theories going around at the moment relate to this virus being somehow engineered with intent.
"[14] According to emails obtained by BuzzFeed News and the Washington Post through FOIA, in the weeks before the publication of the paper, the authors held a teleconference with Anthony Fauci and Francis Collins organized by Jeremy Farrar, with 11 other scientists, including coronavirologists Marion Koopmans and Ron Fouchier.
However, since we observed all notable SARS-CoV-2 features, including the optimized RBD and polybasic cleavage site, in related coronaviruses in nature, we do not believe that any type of laboratory-based scenario is plausible.