Ancient DNA in Old Books: The Deadly Virus That Shaped Farming for Millennia

In September 2026, scientists made a surprising discovery: deadly virus DNA was hidden inside the pages of famous medieval manuscripts. By studying this ancient DNA, they pushed the known history of the sheeppox virus back more than 3,500 years, much older than anyone thought before. This story shows how old books, made from animal skin, can act like biological time capsules, preserving clues about diseases that affected sheep herds in the Bronze Age, the Roman world, and medieval Europe.

Researchers took tiny samples from the parchment pages of historic manuscripts, including the famous York Gospels, which are about 1,000 years old. Instead of just reading the text, they extracted DNA from the animal skins used to make the pages. What they found was sheeppox virus DNA, the virus that causes a severe and often deadly disease in sheep. This hidden viral DNA was detected in several important books, such as the York Gospels in England and the Corpus Glossary at Cambridge, one of the earliest English dictionaries, as well as other medieval books from libraries in the UK, France, and Central Europe. In some books, many different pages tested positive, suggesting that infected animals were commonly used to make parchment.

Before this study, most records of sheeppox came from modern veterinary history. But by combining data from medieval manuscripts with even older samples, like Bronze Age sheep teeth from ancient pastoralist sites, the team traced sheeppox back at least 3,700 years, with some estimates around 5,000 years. Using 21 ancient viral genomes from about 1700 BCE to the early modern period, they showed that the main capripoxviruses, including sheeppox, goatpox, and lumpy skin disease virus, split apart between 11,500 and 3,700 years ago. This timeline matches the spread of domesticated sheep and early farming societies across Eurasia. In short, sheeppox has been a threat to sheep herds since the Bronze Age, not just in recent centuries.

Sheeppox is not a mild disease. It causes high fever, painful skin lesions all over the body, weakness, reduced wool and meat quality, and death, especially in young lambs. Even today, outbreaks cause serious economic losses for farmers, for example in countries like Greece. The ancient genomes gave scientists two important insights. First, the virus genome is very stable. Unlike smallpox in humans, sheeppox has changed very little over thousands of years. Second, the key adaptations happened earlier. The main genetic changes that allowed sheeppox to infect sheep likely occurred before this 3,500‑year window, during early domestication. This deep history helps researchers understand which parts of the virus are most important, which can guide better vaccines and control strategies for today’s outbreaks.

Medieval books were not made from paper, but from parchment, which is specially prepared skin of sheep, goats, and cattle. When an infected animal was slaughtered, its skin could still carry traces of the virus. Over centuries, these skins were turned into pages, and the viral DNA became trapped inside the parchment. Modern DNA techniques can now read this hidden genetic information without damaging the text or artwork. Interestingly, sheeppox DNA was also found on some calfskin and goatskin pages, suggesting either rare cross‑species infections or contamination during parchment production. As one researcher put it, libraries and archives around the world may hold genetic traces of past animal disease outbreaks, waiting to be discovered.

This discovery creates a new kind of history, where scholars study both the words and art in manuscripts and the biological stories hidden in the animal skins. Medieval manuscripts are now seen as dual archives, preserving religion, law, science, and literature, while also recording the health of livestock and the spread of diseases over millennia. This fits into a larger revolution in ancient DNA research, where scientists recover pathogen genomes from skeletons, teeth, and artifacts to rewrite the history of epidemics.

Medieval manuscripts are more than beautiful old books. They are time machines that preserve not just prayers and stories, but also the genetic footprints of diseases that shaped human and animal history. By reading the hidden DNA in parchment, scientists have shown that the sheeppox virus has threatened sheep herds for over 3,500 years, rewriting our understanding of this deadly disease. And this is just the beginning: libraries and archives worldwide may still hold many more ancient viral secrets, waiting for the next generation of researchers and storytellers to uncover them.

The original research paper behind this news is:

Title:
3,500 years of sheeppox virus evolution inferred from archaeological and codicological genomes

Authors (lead team):
Louis L’Hôte and Kevin G. Daly, University College Dublin, with international collaborators including The Pirbright Institute.

Journal:
Science Advances

Publication date:
2 September 2026

DOI (direct link to the paper):
https://doi.org/10.64898/2026.02.23.707469[pirbright.ac

In this study, the team screened more than 750 samples from across Eurasia, spanning about 14,000 years, and reconstructed 22 ancient sheeppox virus genomes, including DNA taken directly from medieval manuscript parchment.