DNA recovered from mummies in northern Chile has provided the strongest scientific evidence yet that European colonization introduced smallpox to the Americas, confirming what historians have long believed from written records.
Researchers identified genetic traces of the virus in human remains from the Camarones archaeological site in northern Chile. The findings, published Thursday in the journal Science, offer the clearest molecular link between smallpox in the Americas and virus strains that once circulated in Europe.
Smallpox was one of history’s deadliest infectious diseases before the World Health Organization declared it eradicated in 1980 through a global vaccination campaign.
The virus killed about one-third of infected people and left many survivors with permanent scars. Indigenous communities in the Americas were especially vulnerable because they had never been exposed to the disease.
Genomes trace the virus to Europe
For the study, geneticist Shigeki Nakagome of Trinity College Dublin and his colleagues analyzed DNA from 13 bone samples recovered at the Camarones archaeological site. The team found evidence of smallpox infection in the leg bone fragments of an adult man and an adult woman.
Radiocarbon dating and genetic analysis showed the two individuals likely died between 1492 and 1631, during the early decades of European colonization in the Americas.
Researchers compared the virus genomes with known smallpox strains from other regions. The Chilean samples fit between medieval European strains and later versions of the virus, providing strong genetic evidence that the smallpox lineages circulating in the Americas descended from European ancestors.
Ancient DNA from Chilean mummies has provided the strongest genetic evidence yet that European colonization brought smallpox to the Americas.
Researchers identified the virus in human remains dating to the early colonial period and traced it to European lineages. pic.twitter.com/0I9M06S0XS
— Tom Marvolo Riddle (@tom_riddle2025) July 31, 2026
Patricia Foster, a biologist at Indiana University who was not involved in the study, said the research provides long-sought biological proof for a theory that had previously relied mainly on historical accounts. “Nobody would ever question that smallpox came to this hemisphere from colonization, but this proves it,” Foster said.
Researchers investigate how the disease spread
Researchers said it remains uncertain who first introduced the virus to the Americas. European settlers arrived in several waves after Christopher Columbus reached the Caribbean in 1492, while later expeditions expanded into South America. The virus may also have spread through Africa during the transatlantic slave trade before reaching the continent.
The discovery also raises new questions because the infected individuals lived in a region where no previous evidence of smallpox had been found. Researchers suggest the disease may have spread south through Indigenous trade networks that existed long before Europeans arrived.
The genetic analysis also revealed how the virus evolved. Researchers found that smallpox gradually lost certain genes, making it better adapted to infect humans.
Findings highlight the human toll
The two individuals examined were between 18 and 35 years old, and researchers believe smallpox was the likely cause of their deaths. Study co-author Constanza de la Fuente Castro, a biological anthropologist at the University of Chile, said the findings underscore the devastating impact of the disease on Indigenous populations.
“It wasn’t just cultural or demographic. It’s literally written into biological evidence that we can still recover and read today,” de la Fuente Castro said.
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