Smallpox killed about one-third of those infected before eradication
Historical accounts from the colonial period have long described how smallpox swept through the Americas after European contact, killing millions of Indigenous people who had no prior immunity to the virus. Those accounts, drawn from administrative records, missionary reports, and other colonial-era writings, have now received genetic corroboration from an unexpected source.
Researchers analyzing DNA extracted from ancient mummies in Chile have produced what they describe as the firmest genetic evidence to date linking smallpox in the Americas to the virus that existed elsewhere in the world, said geneticist Shigeki Nakagome of Trinity College Dublin.
Before its eradication in 1980 through global vaccination campaigns, smallpox was among the deadliest diseases in human history. The virus killed roughly one-third of everyone it infected, and survivors were often left with deep, permanent scarring.
The new genetic evidence does more than confirm the historical record, Nakagome said. It also sheds light on the pathways the virus traveled as it moved from colonizers into remote Indigenous communities.
“Now there’s scientific evidence for the spread: An analysis of Chilean mummies provides the strongest genetic link yet to the virus as it existed outside of the Americas, and provides a better picture of how it reached remote populations through colonization,” Nakagome said.