Diverse variola virus (smallpox) strains were widespread in northern Europe in the Viking Age.

The article informs on a research on identification of variola virus in archaeological remains from the Viking Age that reveals new information about the origin of variola virus and its evolution in human populations. It mentions that evolutionarily sucnumber of functional genes is generally reduced in orthopoxviruses with narrow host ranges. It also mentions that ancient virus sequences recovered from archaeological remains provide direct molecular evidence of past infections.