Study pushes origin of smallpox another 2,000 years

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By Cara Murez

Health Day Reporter

WEDNESDAY, Jan. 11, 2023 (HealthDay News) — While the origins of smallpox have remained a mystery for centuries, researchers now believe they date 2,000 years earlier than previously thought.

Until recently, the earliest genetic evidence for smallpox, the variola virus, dates back to the 17th century. And in 2020, researchers found evidence of it in the tooth remains of Viking skeletons, forcing its existence 1,000 years earlier.

Now, Italian scientists have used a mathematical equation to locate the beginnings of smallpox, and together with the pockmarks seen on ancient Egyptian mummies, they’ve pushed the virus’ genesis back 3,800 years.

“The variola virus may be much, much older than we thought,” said the study’s first author, Dr. Diego Forni, from the IRCCS Eugenio Medea Scientific Institute in Italy.

“This is important because it confirms the historical hypothesis that smallpox existed in ancient societies. It is also important to consider that there are some aspects in the evolution of viruses that should be considered in this type of work,” Forni said in a Microbiology Society press release.

Smallpox was relatively recently eradicated, killing at least 300 million people in the 20th century.

In the new study, the researchers found that different smallpox strains all descended from a single common ancestor. A small fraction of the genetic components found in Viking Age genomes survived even into the 18th century.

To estimate the origin of the virus, the researchers then considered something called the “time-dependent rate phenomenon.”

This means that the speed of evolution depends on how long it is measured. That means viruses appear to change faster over a short period of time and slower over a longer period of time, something the study’s authors say is well documented in DNA viruses.

By using a mathematical equation to account for the time-dependent rate phenomenon, the research team estimated that the first appearance of smallpox could date back to Egyptian times: ancient mummies, including the 1157 B.C. Pharaoh Ramses V. who died had suspicious scars.

The results were published online on January 9 in the journal Microbial Genomics.

More information

The US Centers for Disease Control and Prevention has more on smallpox.

SOURCE: Microbiology Society, press release, January 9, 2023

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Study pushes origin of smallpox another 2,000 years
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