Turns out, some medieval manuscripts are more than just old books: they're time capsules for ancient diseases.
Researchers found DNA from the sheeppox virus in the 1,000-year-old York Gospels and other parchments made from animal hides.
This means infected sheep were likely used to make these pages, giving us a peek into how long this virus has been around: more than 3,500 years!
Sheeppox barely changed over 3,700 years
The team also studied ancient sheep teeth and discovered traces of sheeppox going back more than 3,700 years.
The study shows that while many viruses change fast, sheeppox has barely changed at all.
With help from more than 30 institutions like Trinity College Dublin and Cambridge University, researchers showed that even cultural treasures like old books can teach us a lot about how diseases stick around and shape history.