Scientists found the conclusions of the WHO report to be helpful but noted that more work was needed. It also stated that a laboratory origin for the virus was "extremely unlikely." Echoing the assessment of most virologists, the report determined that the virus most likely had a zoonotic origin in bats, possibly transmitted through an intermediate host. In March 2021, the findings of this study were published online in a report to the WHO Commissioner-General. In January 2021, the World Health Assembly (decision-making body of the World Health Organization, WHO) commissioned a study on the origins of the virus, to be conducted jointly between WHO experts and Chinese scientists.
Health authorities and scientists internationally state that as with the 2002–2004 outbreak of SARS-1, efforts to trace the specific geographic and taxonomic origins of SARS-CoV-2 could take years, and the results could be inconclusive.
Initial genome sequences of the virus showed little genetic diversity, although subsequently a number of stable variants emerged (some spreading more vigorously), indicating that the spillover event introducing SARS-CoV-2 to humans is likely to have occurred in late 2019. Research is ongoing as to whether SARS-CoV-2 came directly from bats or indirectly through any intermediate hosts. SARS-CoV-2 has close genetic similarity to multiple previously identified bat coronaviruses, suggesting it crossed over into humans from bats. Many other explanations, including several conspiracy theories, have been proposed about the origins of the virus. Most scientists say that as with other pandemics in human history, the virus is likely of zoonotic origin in a natural setting, and ultimately originated from a bat-borne virus. There are several ongoing efforts by scientists, governments, international organisations, and others to determine the origin of SARS-CoV-2, the virus responsible for the COVID-19 pandemic.
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