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DNA studies prove smallpox was present among the Vikings

Additional research has also investigated the source of a vaccine used in the Civil War
DNA studies prove smallpox was present among the Vikings hero image

Smallpox starts with flu-like symptoms and can lead to severe back pain and the appearance of lesions, which turn into pus-filled blisters and eventually fall off, leaving deep, pitted scars. There’s no cure or treatment, but most people who get it survive—albeit with severe scars which in extreme instances can cause blindness.

Smallpox has been a public health scourge for centuries. Recorded outbreaks usually accompanied increased trade, foreign occupations, and colonization.

Control efforts began with variolation and grew into a worldwide World Health Organization vaccination plan. North America was declared smallpox-free in 1952, followed by Europe in 1953 and South America in 1971. The world was declared free of smallpox in 1980, and most discussion these days about the diseases is what to do with the small number of smallpox samples residing in labs for research purposes.

Despite its eradication, genetics science continues to teach us about this historic disease.

A recent study published in Science found that smallpox strains were widespread in northern Europe during the age of the Vikings—around the 7th century.

A team of researchers from the University of Cambridge and the University of Copenhagen recovered viral sequences from 11 northern Europeans who lived during that time and reconstructed near-complete virus genomes from several of them. The finding pins the existence of the virus some 1,000 years earlier than the oldest known evidence.

“These sequences, combined with early written records of VARV epidemics in southern and western Europe, suggest a pan-European presence of smallpox from the late 6th century,” the authors wrote. “The ancient viruses are part of a previously unknown, now-extinct virus clade and were following a genotypic evolutionary path that differs from modern VARV. The reduction in gene content shows that multiple combinations of active genes have led to variola viruses capable of circulating widely within the human population.”

What is not yet clear, the researchers added, is if the infections produced symptoms similar to those found in more recent times.

Another recent study published in Genome Biology used metagenomic sequencing to identify smallpox vaccine strains from the Civil War.

In the study, the authors noted that vaccinations were required for both Northern and Southern soldiers. Researchers sampled the organic and non-organic parts of five vaccination kits, which typically included lancets, mixing plates, and scab collection boxes.

Results from shotgun sequencing allowed researchers to rebuild the mitochondrial genomes for the human donors of three samples and determine haplogroups, which suggested the donors.

“The haplogroups H1b, T2b4f and U5b1 are most frequently found in west Eurasia, suggesting that the vaccine donors were likely of European ancestry and not African American even though African American children were frequently used for vaccine propagation in the southern states during the American Civil War,” the authors wrote.

The results further showed that “vaccination was a uniquely human process,” with vaccine material being produced in humans and then transferred to patients—a process which later changed in response to public health concerns about disease spread. At the time, however, there were no advertised vaccination kits—instead, kits were made to order, and similarity in the strains surveyed here and those from a 1902 strain suggests a common material source which was present in the Philadelphia area, which at the time was a center of medical training and research.

“The clear identification and reconstruction of near-complete genomes of VACV from these vaccination kits, which were in use during the American Civil War era, indicates that these strains were circulating within humans and via physician networks prior to the twentieth century,” the report concluded.

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