Story highlights Oldest known sample of the variola virus has been found in the DNA of a child mummy

This latest research suggests that smallpox is much more recent than we might think

(CNN) The oldest known sample of the smallpox-causing variola virus has been found within the DNA of a 17th-century child mummy. The mummy was found in a crypt beneath a Lithuanian church, according to a new study in the journal Current Biology. The finding shortens the timeline for how long smallpox may have afflicted humans.

Smallpox , a contagious and sometimes fatal infectious disease, is the only human disease to be eradicated by vaccination. It is also the first disease that a vaccine was developed to combat.

The disease has previously thought to have affected humans as far back as ancient Egypt due to pockmarked scarring on mummies that are 3,000 to 4,000 years old. But researchers knew that smallpox may not be that old; that type of scarring can also be associated with chickenpox or measles, according to study co-author Hendrik Poinar, director of the Ancient DNA Center at McMaster University in Hamilton, Ontario.

This latest research suggests that smallpox, which was eradicated in 1980, could be much more recent.

"This study suggests that all 20th-century variola strains and our 17th-century strain share a common ancestor in the late 16th century or early 17th century, which is more recent than we would expect for a virus that has supposedly been afflicting humans for millennia," said Ana Duggan, lead study author and post-doctoral fellow at the McMaster Ancient DNA Center. "However, this date correlates with historical records which show that there is little suggestion of epidemic smallpox in Europe before the 16th century."

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