Smallpox has left an unmistakable mark on human history, killing at least 300 million people in the 20th century alone. Although this virus is well-known, its origin is still unknown.
A team of Italian scientists has now pushed previous estimates of smallpox outbreaks forward by 2,000 years, adding historical evidence that suggests the disease has plagued human society since ancient times, when pharaohs ruled. I verified it.
In recent years, advances in gene sequencing technology have enabled us to analyze fragments of ancient viral DNA in greater detail, bringing us closer to when and where smallpox originated.
Thanks to a lucky discovery in Lithuania in 2016, scientists were able to trace smallpox to the 16th century using viral DNA extracted from the remains of children. In 2020, viral DNA from Viking-era skeletons pushed the last appearance of smallpox back several years, to sometime before 1050 AD, providing genetic evidence.
However, historical sources suggest that something like smallpox struck ancient societies much earlier. There are descriptions of disease-like symptoms in 4th-century Chinese writings, and smallpox-marked Egyptian mummies also suggest an epidemic of smallpox 3,000 to 4,000 years ago.
But finding definitive genetic evidence (like a viral molecular fingerprint) to support this theory has been difficult.
With enough samples to compare against, scientists can still infer a lot about the past and evolutionary history of viruses. You can see how viruses have changed over time, and how fast or slow their genes mutate. From there, scientists can unwind the ‘molecular clock’ and deduce when the ancestral version of the virus existed.
Smallpox is caused by the variola virus (VARV). In this study, led by Diego Forni, a bioinformatician at the Scientific Institute for Research, Hospitalization and Healthcare (IRCCS) in Italy, a team led the genetic analysis of 54 VARV samples collected from previously published papers and research databases. I re-examined the array.
These include four ancient VARV genomes from the Viking Age, two historical VARV genomes from the 17th and 18th centuries, and 48 modern VARV sequences prior to the 1980 eradication of smallpox.
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