Ancient DNA shows Europeans introduced smallpox to Americas

Scientists have discovered the first genetic evidence that smallpox was introduced to the Americas by European colonizers, according to a new study published on July 30, 2026. The breakthrough came from the analysis of viral DNA recovered from two 500-year-old Inca mummies found in northern Chile.

The mummified remains, an adult woman and an adult man, were recovered from the Camarones 9 archaeological site. Radiocarbon dating indicates the individuals died between 1492 and 1631. Researchers from Trinity College Dublin and the University of Chile identified fragments of the variola virus, which causes smallpox, in bone samples from both individuals. The team was initially studying human population history and did not expect to find pathogen DNA.

Analysis showed the two viral genomes were nearly identical, suggesting the individuals were infected during the same outbreak or by the same circulating strain. The strain, named CAM9 by the researchers, represents an extinct lineage that fits evolutionarily between medieval European strains and modern variants. This provides the first molecular confirmation that Europeans brought smallpox to the Americas during the colonial period....