Smallpox Has Plagued Humans Since Ancient Egyptian Times, New Evidence Confirms

Published:30 Jan.2023 Source:Microbiology Society

By comparing the genomes of modern and historic strains of variola virus, researchers at the Scientific Institute Eugenio Medea and University of Milan in Italy have traced the evolution of the virus back in time. They found that different strains of smallpox all descended from a single common ancestor and that a small fraction of the genetic components found in Viking-age genomes had persisted until the 18th century.

They also worked out an estimate for when the virus originated. In their estimate, the researchers accounted for something called the ‘time-dependent rate phenomenon’ This means that the speed of evolution depends on the length of time over which it is being measured, so viruses appear to change more quickly over a short timeframe and more slowly over a longer timeframe. The phenomenon has been well-documented in DNA viruses like variola. Using a mathematical equation, scientists can account for the time-dependent rate phenomenon to give more accurate dates for evolutionary events, such as the appearance of a new virus. This gave the team a new estimate for the first emergence of smallpox: more than 3,800 years ago. Just as historians have long suspected. The researchers hope these findings will settle a longstanding controversy and provide new insight into the history of one of humanity's deadliest diseases.