Genomic Evidence Links Smallpox to European Introduction in Americas

Viral sequences extracted from Chilean mummies have provided the first direct genomic evidence confirming that smallpox was introduced to the Americas by Europeans. Published online on July 31, 2026, in Nature, the study analyzed ancient DNA from individuals who died in the 14th and 15th centuries, predating European arrival. The research team successfully sequenced fragments of the variola virus, the causative agent of smallpox, from these ancient samples. This groundbreaking discovery challenges previous assumptions about the origins and timeline of smallpox in the New World.

Prior to this research, the introduction of smallpox to the Americas was largely inferred from historical accounts and epidemiological studies, which suggested a post-Columbian introduction. However, the precise timing and source remained subjects of debate. The new genomic data offers a definitive link, demonstrating the presence of smallpox in South America before the arrival of Christopher Columbus in 1492. The genetic makeup of the variola virus found in the mummies was compared to modern and historical strains, revealing a close relationship to European variants. This suggests that European explorers and colonists were the vectors for the disease, which subsequently devastated indigenous populations who had no prior immunity.

The methodology involved sophisticated ancient DNA extraction and sequencing techniques, overcoming the challenges of DNA degradation over centuries. The researchers employed advanced bioinformatics to reconstruct viral genomes from fragmented DNA. The study's findings are significant not only for understanding the history of infectious diseases but also for informing public health strategies and historical interpretations. The devastating impact of smallpox on indigenous communities in the Americas is well-documented, leading to massive population decline and profound societal disruption. This research provides a crucial piece of the puzzle, solidifying the role of European introduction in this tragic chapter of history.

This study, published in Nature with the DOI 10.1038/d41586-026-02366-y, represents a major advancement in paleovirology and the study of disease transmission. By combining archaeological evidence with cutting-edge genomic analysis, scientists can now trace the historical spread of pathogens with unprecedented accuracy. The implications extend beyond smallpox, offering a template for future investigations into the origins of other diseases that impacted human populations throughout history. The research team's ability to recover and analyze viral genomes from ancient human remains underscores the power of molecular techniques in rewriting our understanding of the past.