Smallpox, one of the most devastating human diseases, killed between 300 million and 500 million people in the 20th century alone. We recovered viral sequences from 13 northern European individuals, including 11 dated to ~600–1050 CE, overlapping the Viking Age, and reconstructed near-complete variola virus genomes for four of them. The samples predate the earliest confirmed smallpox cases by ~1000 years, and the sequences reveal a now-extinct sister clade of the modern variola viruses that were in circulation before the eradication of smallpox. We date the most recent common ancestor of variola virus to ~1700 years ago. Distinct patterns of gene inactivation in the four near-complete sequences show that different evolutionary paths of genotypic host adaptation resulted in variola viruses that circulated widely among humans.

天花是最严重的人类疾病之一，仅在20世纪，它就造成3亿至5亿人死亡。我们从13个北欧个体中恢复了病毒序列，其中包括11个约在公元600-1050年，与维京时代重叠，并为其中四个重建了近乎完整的天花病毒基因组。这些样本比最早的确诊天花病例早了约1000年，并且序列显示了现已消灭的现代天花病毒姐妹姐妹进化枝，它们已经在根除天花之前流通。我们将天花病毒的最新共同祖先追溯到大约1700年前。在四个接近完整的序列中，基因灭活的不同模式表明，基因型宿主适应的不同进化途径导致天花病毒在人类中广泛传播。