The SARS-CoV-2 virus of the COVID-19 pandemic, that is presently devastating the entire world, had been active well before January of this year, when its pathogenic potential exploded full force in Wuhan. It had caused the onset of small disease outbreaks in China, and probably elsewhere as well, which failed to reach epidemic potential. The distant general origin of its zoonosis can be traced back to the ecosystem changes that have decreased biodiversity, greatly facilitating the contacts between humans and the animal reservoirs that carry pathogens, including SARS-CoV-2. These reservoirs are the bats. The transition between the limited outbreaks that had occurred through 2019 and the epidemic explosion of December-January was made possible by the great amplification of the general negative conditions that had caused the preceding small outbreaks. In the light of what we have now learned, the explosion was predictable, and could have happened wherever the conditions that had allowed it, could be duplicated. What could not have been predicted was the second transition, from epidemic to pandemic. Research has now revealed that the globalization of the infection appears to have been caused by a mutation in the spike protein of the SARS-CoV-2, that has dramatically increased its transmissibility.
History of the COVID-19 pandemic: Origin, explosion, worldwide spreading