The evolution of the deadliest virus in human history — smallpox — is only partly understood. Like the novel coronavirus and many other disease-causing viruses, smallpox seems to have originated in animals, probably rodents, and spilled over to humans, probably thousands of years ago. It is not an ancestor of the modern smallpox virus, but an evolutionary dead end. Putting those facts together caused one prominent smallpox specialist to suggest that the modern virus might have become more deadly as it evolved. Pox viruses are not closely related to coronaviruses, and the research has no direct application to the current spread of the novel coronavirus.

Source: International New York Times July 23, 2020 18:00 UTC