Findings of a new study offer a new timeline for smallpox, a deadly disease caused by the variola virus.

Smallpox Not An Ancient Disease

Researchers have found evidence suggesting that the pathogen responsible for millions of deaths worldwide before it was finally declared eradicated in 1980 may be a modern killer and not an ancient disease as previously believed.

The disease had long been believed to have emerged among humans thousands of years ago, afflicting people in India, Egypt, and China. Some historical accounts even suggest the Egyptian pharaoh Ramses V, who passed away in 1145 B.C., had been struck by smallpox.

Disease Could Be Much Younger Than Previously Thought

For the study that involved the genetic analysis of the viral DNA taken from the partially mummified remains of a child dating back from the 17th century, researchers found that the smallpox could be just some hundreds of years old.

The researchers obtained clearance from the World Health Organization in Geneva to extract heavily fragmented DNA from a mummified Lithuanian child, who likely died between 1643 and 1665, when Europe was hit by several smallpox outbreaks.

Analysis Of Ancient DNA Sheds Light On Evolution Of Smallpox

The researchers captured, sequenced, and completely reconstructed the smallpox DNA and then compared the strain to those from modern samples dating between 1940 and 1977, when the last known case of the disease occurred in Somalia.

The findings showed that the evolution of the smallpox virus happened more recently than previously believed and that the ancestor of all available smallpox viral strains were no older than 1580 albeit it is not yet clear what animal is the true reservoir of the pathogen and when the virus first jumped from animals to humans.

The researchers, who published their findings in the journal Current Biology on Dec. 8, also found that the evolution of the pathogen into two circulating strains, the variola major and minor, occurred after 1796, after scientist Edward Jenner came up with a vaccine.

"Our data clearly show that the VARV lineages eradicated during the 20th century had only been in existence for ∼200 years, at a time of rapidly expanding human movement and population size in the face of increasingly widespread inoculation and vaccination," the researchers wrote in their study.

The WHO has only allowed two laboratories to store samples of smallpox, one in Atlanta in the United States and another in Russia. The agency regularly inspects these repositories to ensure they are safe and secure.

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