Peter Ben Embarek, PhD, the leading animal disease expert at the World Health Organization (WHO), said the investigative team looked into four main scenarios about how SARS-CoV-2, the virus that causes COVID-19, initially spread to humans, according to Reuters.
The first scenario theorizes a single person was exposed to SARS-CoV-2 through direct contact with a horseshoe bat. The virus might have been circulating in humans for some time before infecting people in Wuhan.
The second, and most likely scenario, involves transmission to humans through an unknown intermediary species. Liang Wannian, PhD, an expert with China’s National Health Commission, told CNBC that pangolins were potential candidates but other animals may have also served as reservoirs.
A third possibility is that COVID-19 originated under the first or second scenarios and that the virus was transmitted via frozen foods. Chinese experts associate later COVID-19 clusters to imported frozen foodTrusted Source.
However, investigators found that the fourth and least likely scenario is that SARS-CoV-2 was leaked from the Wuhan Institute of Virology, which is known to have studied captive coronaviruses.