‘Severe pneumonia of unknown cause’ cases were recognised in Wuhan on 9/12/2019 and announced by China on 30/12/2019. The causative agent, SARS-CoV-2, was published on 7/1/2020 along with the first full-length sequence on 10/1/2020. WHO called a global health emergency (30/1/2020), declared a pandemic (11/3/2020), and announced the emergency’s end on 5/5/2023.
A WHO-China Study Group was formed to determine likely origins and to guide further studies, focusing on animals and the environment, human epidemiology, and analyses of viral sequences. The main SARS-CoV-2 origins hypotheses were explored: animal (most likely bat) origin and transmission by intermediate animals to humans, direct animal transmission (e.g. bats directly to humans), possible laboratory leaks, and acquisition from contaminated frozen foods.
The early cases were mostly associated with central Wuhan’s Huanan wet market, with presentations to nearby hospitals. Over the next two months, it spread throughout Wuhan, Hubei province and world-wide. The review of early SARS-CoV-2 sequences, epidemiology, environmental analyses and the known market presence of animals prior to the outbreak confirmed the Huanan market as the outbreak epicenter. Concerns were raised that the time taken to continue origins studies was slipping away (due to ongoing tensions between nations and the WHO), especially those needed to investigate source wild/farmed animal infection with coronaviruses, and investigation of people involved in such animal husbandry.
The evidence of SARS-CoV-2 genomic similarities in bats, characteristics of bat SARSr-CoVs, coronavirus genomic plasticity, recent historical emergence of other human coronaviruses, wet market analyses, and ongoing lack of available evidence of a laboratory source means that in vivo coronavirus recombination/mutation in host and intermediate animals remains the most likely origin of SARS-CoV-2. Recent and controversial analyses of environmental viral and animal genetic material collected from the Huanan market places raccoon dogs (and other animals known to be SARS-CoV-2 susceptible sold at the market) as possible animal reservoirs.
The direct ancestor of SARS-CoV-2 in bats and any intermediate animal(s) remains unidentified, noting that such conclusions with SARS in 2003 took over a decade. SARS, MERS, SARS-CoV-2, and other known human coronaviruses suggest that coronaviruses remain an ongoing pandemic threat.