Scientists find the oldest DNA of the smallpox virus

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This surprising discovery made through the mummified body of a child who died in the eighteenth century can help scientists understand the mysterious history of this deadly pathogen.

Some specimens of this virus exist only in the well-protected freezers of some laboratories, preserved for studies since the eradication of this infection, with its greatest outbreak in the late 1970s, the result of vaccination campaigns.

But until now, the source of the virus remains unknown and the discovery of viral DNA on the skin of the mummified body that was placed in a grave under a Lithuanian church could end the mystery about the infectious disease, according to scientists.

This finding was published in the current scientific journal Current Biology.

The DNA sequence of this ancient pathogen would indicate, among other things, that the infection has emerged among humans more recently than previously thought and also reveals that the microbe has undergone several mutations over the years.

“There are indications that 3,000 to 4,000-year-old Egyptian mummies had marks that appeared to be affected skins, interpreted as resulting from smallpox-like pimples”, said Ana Duggan, a scientist at McMaster University in Canada, the lead author of this study.

“The latest finding really questions this interpretation and suggests that the history of smallpox in human populations may be inaccurate”, he added.

Scientists reconstituted the complete genome of the strain found in the mummified body and compared it with the smallpox viruses dating from the mid-eighteenth century and also the period preceding the eradication of the infection in the late 1970s.

It was concluded that the viruses had a common viral ancestor, which appeared between the years 1588 and 1645, which coincides with a period of exploration, migration and colonization that could have contributed to the spread of smallpox around the world.

With this thesis, perhaps the Egyptians of the time of Ramesses have not suffered with the smallpox virus, but with chickenpox or measles, they indicated the scientists.

In addition, the reconstruction of the genome of this ancient virus, enabled a more accurate dating of the evolution of the disease, scientists have been able to identify distinct periods of evolution of the virus.

They cited a clear example, recorded at the time when the English physician Edward Jenner created his vaccine against smallpox in the eighteenth century.

At this time, the virus appeared to have split into two strains, suggesting that vaccination may have put pressure on the pathogen for its adaptation.

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