The origins of SARS-CoV-2: still to be determined - Bulletin of the Atomic Scientists
SARS in 2003 and MERS in 2012 resulted from natural spillover events in which animals infected humans with coronaviruses. In both cases, the viruses-and/or antibodies to the viruses were identified both in humans and in animals, and humans with occupational exposures to animals exhibited higher rates of seropositivity to the viruses than the general human population. So far, studies attesting to natural spillover of COVID-19 fail to meet these criteria.