 | Researchers collected DNA from viruses in the remains of northern Europeans living during the Viking Age, some of whom were likely Vikings themselves. They were infected with extinct but related versions of the variola virus that causes smallpox. It is still uncertain when the virus that causes smallpox first began to infect people. The disease is estimated to have killed as many as 500 million people. |
 | Researchers isolated viral DNA from human teeth and bones, like this 1,200-year-old smallpox-infected Viking skeleton found in Öland, Sweden. The team reconstructed nearly complete genetic blueprints of four of the 11 ancient viruses. During that period, smallpox may have been widespread throughout Europe and could have caused serious disease. |
