In 2017, researchers rubbed soft vinyl erasers across the pages of the York Gospels — a book of the four Gospels in Latin, made at Canterbury around the year 1000, still used for oath-taking when bishops are installed at York Minster today — and sequenced the shavings to identify the animals used to make the book. The technique, called eZooMS, collects collagen and DNA from skin cells embedded in the hide without cutting anything. Nearly a decade later, those stored libraries were re-analysed — and in three folios, they turned up viral DNA from sheeppox, a disease of sheep and goats related to smallpox.

Curiously, the York Gospels are calfskin, not sheepskin. Sheeppox has no documented natural hosts in cattle. Yet the DNA was there, embedded in hides that no medieval calf had directly encountered. A study published earlier this month in Science Advances traces the pathogen back at least 3,700 years and shows that Europe once carried its own distinct sheeppox lineage — a lineage now extinct. The virus forcing Greece to cull hundreds of thousands of animals today is a different one. The obstacles to stopping it are not.

The study, led by Louis L’Hôte, Kevin Daly and 35 colleagues, screened 754 samples spanning more than 14,000 years of Eurasian material and assembled 22 ancient sheeppox genomes. Seventeen detections came from medieval parchment — books and documents from Britain, the Upper Rhine, Austria and France, produced between the early 8th and the 14th century. The York Gospels gave three positive folios; the Corpus Glossary at Cambridge, a manuscript of the Epistles of Paul from around 700 CE, and several folios from the Speculum Historiale historically associated with the Vinland Map were among the finds. The study also notes what appear to be pox-like lesions on the membrane of the Codex Amiatinus — the oldest complete surviving Latin Bible, made at Wearmouth-Jarrow in Northumbria around 700 CE — though no viral DNA was recovered from it.

The published count understates the hit rate. Daly told me the team screened roughly 80 parchments in total and found sheeppox reads in 32. Two in five medieval books they examined carry traces of a livestock epidemic. “When you pick up a book, you’re picking up a flock of sheep or herd of cattle,” the Leicester historian Joanna Story, a co-author, told Science .

Ten positive folios came from cattle parchment, four from goats and three from sheep — most of them calfskin, despite sheeppox having no confirmed natural host in cattle. Daly thinks two explanations probably hold: many positive parchments carry sheep DNA alongside the virus, pointing to contamination from collagen or glue made from sheep during production, but one Canterbury folio, TCCL02, gave about 400 sheeppox reads with no sheep DNA beside them and “would appear to be a genuine infection.” His team now wants to find cattle hides bearing both SPPV DNA and visible pox lesions.

The original York Gospels sampling was led by Sarah Fiddyment in collaboration with conservators at York Minster. That any viral DNA survived lime, scraping and a thousand years of handling still surprises outside observers. “I couldn’t have imagined they’d get all this data from parchment,” Nicolás Rascovan of the Pasteur Institute told Science .

Europe’s Own Sheeppox Is Extinct

The medieval parchment finds were not the oldest. Two sheep teeth from Bronze Age sites in Kazakhstan and Russia yielded sheeppox genomes dated to roughly 1875–1645 BCE and 1336–1130 BCE — the oldest poxvirus genomes ever recovered — about 3,400 years older than any previously known. Both come from intensive sheep-husbandry economies on the Eurasian steppe.

These genomes place the emergence of a sheep-specific capripoxvirus at around 5,000 years ago, roughly when steppe herders began breeding flocks intensively for wool and moving them across Eurasia. That timing fits a broader pattern: farming concentrated susceptible animals, and novel pathogens followed. The same logic applies to measles, brucellosis and several other livestock diseases.

What happened next is the unusual finding. Nine genes that are inactivated in modern sheeppox are already broken in the 3,700-year-old Kazakh genome, which means host adaptation was complete within roughly 1,600 years of the split. Variola, the smallpox virus, kept shedding genes throughout its history. Sheeppox stopped early and held still. “Unlike the smallpox virus,” said L’Hôte, “the sheeppox virus genome was very stable over the last few millennia.”

The medieval European viruses belong to a lineage sister to everything circulating today, and that lineage is gone. Modern global diversity coalesces only around 330 years ago. France combined a vaccine with strict movement controls in the early twentieth century and eradicated the disease from its territory. The eradication was real. Why the medieval European lineage disappeared before that — whether it was displaced by modern strains or finished by eradication — is unsettled. Nobody yet has genomes from the intervening 500 years to say.

Is Sheeppox Still a Problem?

Yes. The virus pushing into the Balkans belongs to a modern lineage — distinct from anything in those manuscripts. Between July 2025 and February 2026, five countries reported 1,759 sheep and goat pox outbreaks : Greece 1,549, Bulgaria 183, Romania 21, North Macedonia and Serbia three each. Greece’s previous annual peak was 77. The spread runs west from the Turkish border, consistent with repeated introduction from Turkey, where the disease is endemic. Daly places the Balkan strains in the A1 clade of modern diversity — inside that 330-year-old lineage, arriving into populations that have been naive for a century.

By December 2025, Greece had culled more than 417,000 sheep and goats . Farmers have blockaded border crossings. Compensation runs €132–220 per animal. In October 2025, two people were arrested at the Greek-Turkish border carrying thousands of doses of unlicensed Turkish vaccine — a product Greek veterinary authorities warn is unsafe, only partly effective, and destroys the ability to distinguish vaccinated animals from infected ones.

The European Food Safety Authority concluded in February 2026 that live attenuated sheeppox vaccines give 80 to 100 percent protection, and that adding vaccination to culling would clear the disease from Bulgaria a year sooner. No sheeppox vaccine had been deployed anywhere in the EU in more than thirty years. Prime Minister Mitsotakis rejected mass vaccination in January 2026, arguing that biosecurity on the ground was not being followed well enough for it to work.

The constraint is not the vaccine.

Compliance Has Always Been the Hard Part

It never has been the vaccine. Between 1658 and 1888, a farmer at Louvres, north of Paris, lost nine sheep and dug a pit for them in his own yard. An 1801 order from the Paris police prefecture required carcasses to be buried the same day, skin and wool on, at 1.34 meters depth, outside the town limits.

He dug 60 to 80 centimeters. Less than 60 meters from his front door. Ancient DNA from the teeth confirmed that sheeppox was the killer . More telling was what the bones showed: flay marks on one animal sit unusually high up the limb, higher than ordinary skinning requires. Cutting there lets a skinner take the hide well into the woolled area and leave behind the pocks that erupt on the lower legs, where the fleece is thin. The skin comes off looking clean. Diseased hides were a known route of spread, which is why the ordinances covered them.

Eighteenth-century French veterinarians tried inoculating sheep against the pox on the smallpox model. It mostly worked, but it never caught on beyond scientific circles. A vaccine eventually arrived, combined with enforcement, and eradicated the disease from France in the early twentieth century.

The technology has never been the hard part.