Virus found could re­write small­pox his­tory

China Daily (Hong Kong) - - WORLD - By AGENCE FRANCEPRESSE in Wash­ing­ton

The dis­cov­ery of small­pox DNA in a 17 th cen­tury child mummy may shorten the time­line of the deadly in­fec­tious dis­ease’s his­tory, ac­cord­ing to a study pub­lished on Thurs­day.

Spec­i­mens of the small­pox­caus­ing var­i­ola virus now ex­ist only in se­cured lab­o­ra­tory freez­ers. The highly con­ta­gious and some­times fa­tal dis­ease was fi­nally erad­i­cated in the late 1970s through a world­wide vac­ci­na­tion cam­paign.

But the ori­gins of the virus re­main un­known.

The dis­cov­ery of the small­pox virus within the DNA of a skin sam­ple of the mummy child, found in a crypt un­der- neath a Lithua­nian church, could shed light on how it be­gan and de­vel­oped, re­searchers said in the study pub­lished in the US sci­en­tific jour­nal Cur­rent Bi­ol­ogy.

“There have been signs that Egyp­tian mum­mies that are 3,000 to 4,000 years old have pock­marked scar­ring that have been in­ter­preted as cases of small­pox,” said first au­thor Ana Dug­gan, a post­doc­toral fel­low at the McMaster Univer­sity An­cient DNA Cen­ter in Canada, in a state­ment.

“The new dis­cov­er­ies re­ally throw those find­ings into ques­tion, and they sug­gest that the time­line of small­pox in hu­man pop­u­la­tions might be in­cor­rect.”

The re­searchers re­con­struct- ed the en­tire genome of the an­cient strain of the virus and com­pared it with ver­sions of the var­i­ola virus genome dat­ing from the mid-1900s and be­fore its erad­i­ca­tion in the late 1970s.

Com­mon vi­ral an­ces­tor

They con­cluded that all the sam­ples shared a com­mon vi­ral an­ces­tor that orig­i­nated some­time be­tween 1588 and 1645. Dur­ing that time, ex­plo­ration, mi­gra­tion and col­o­niza­tion would have helped spread small­pox around the globe.

Study co-au­thor Hen­drik Poinar, the di­rec­tor of the An­cient DNA Cen­ter at McMaster Univer­sity, said that con­clu­sion casts doubt on the doc­u­mented his­tor­i­cal ev­i­dence that dates back to Egypt’s Ram­ses V up to the 1500s.

“Are these in­deed real cases of small­pox, or are these misiden­ti­fi­ca­tions, which we know is very easy to do, be­cause it is likely pos­si­ble to mis­take small­pox for chick­en­pox and measles,” Poinar said.

Co-au­thor Ed­ward Holmes, a pro­fes­sor at the Univer­sity of Syd­ney in Aus­tralia, said: “Now we know all the evo­lu­tion of the sam­pled strains dates from 1650, but we still don’t know when small­pox first ap­peared in hu­mans, and we don’t know what an­i­mal it came from, and we don’t know that be­cause we don’t have any older his­tor­i­cal sam­ples to work with.”

“Our his­tor­i­cal knowl­edge of viruses is just the tip of the ice­berg.”

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