Scientists have discovered that ancient manuscripts may hold genetic clues about past disease outbreaks, offering new insights into the history of animal pathogens. One such disease is sheeppox, a highly contagious and often fatal viral infection that primarily affects sheep. While sheeppox was largely eradicated from much of Europe in the 20th century, it still occasionally resurfaces, such as in a recent outbreak in Greece. To better understand how the virus evolved over the past 3,500 years, researchers extracted and sequenced sheeppox DNA preserved in the animal skins used to make parchment for medieval manuscripts. Their findings, published in Science Advances, reveal that such historical documents could be a valuable resource for studying the genetic history of diseases. Louis L’Hôte, a graduate student at University College Dublin and co-author of the study, emphasized the significance of this discovery. “The recording of ancient DNA from pathogens has transformed our understanding of infectious diseases in the past,” he said. “This research shows that parchment can also preserve DNA from animal pathogens, suggesting that archives and libraries worldwide might contain genetic traces of past disease outbreaks.” By analyzing these ancient genomes, scientists can better understand how diseases like sheeppox evolved and how they affected past human and animal societies. The earliest written records of sheeppox date back to the first century CE, when Roman texts described outbreaks of skin lesions, or "pustules," in sheep. By the Middle Ages, references to the disease became more common, appearing in agricultural texts and accounting records across France, Spain, and England. These documents mention frequent and deadly outbreaks referred to as "pockes" or "variola." Although there was a decline in outbreaks in 17th-century France, the disease re-emerged in the 18th and 19th centuries, often with high mortality rates among sheep flocks. In Great Britain, sheeppox did not reappear until 1847, highlighting the varied timelines of disease resurgence across different regions. This research not only helps trace the evolution of sheeppox but also opens the door to exploring other ancient diseases through the study of historical manuscripts. As scientists continue to analyze such sources, they may uncover new details about how past epidemics shaped agriculture, trade, and human history.