In the 10th century, Persian physician Abu Bakr Muhammad ibn Zakariya al-Razi wrote about patients with fever, anxiety and full-body rashes — the first clear medical descriptions of measles. But scientists have never been able to pinpoint when the virus came into being.

Now, genetic sequencing of measles found in a pair of ­century-old lungs suggests the virus existed 1,500 years earlier than previously thought. Researchers from the Robert Koch Institute in Berlin recently posted the results of a newly sequenced measles genome on bioRxiv, which publishes scientific manuscripts before they are submitted to journals.

Figuring out when diseases first arose is tricky work: Researchers must sequence genetic information from various points in history to make educated estimates, and it’s difficult to find well-preserved samples of RNA viruses such as measles.

Until recently, scientists had only analyzed three measles genomes occurring before 1990, and couldn’t track the disease back to earlier than the 11th century.

Then, evolutionary biologist Sébastien Calvignac-Spencer found a pair of lungs in the basement of the Berlin Museum of Medical History at the ­Charité. They had been removed from a 2-year-old after her 1912 death from complications of measles.

After sequencing the older measles RNA, Calvignac-Spencer and colleagues were able to track the virus to as early as 345 B.C. Their findings haven’t yet been peer reviewed, but they could have implications for how scientists treat long-neglected medical archives.

If the measles research does spark a reconsideration of other medical specimens, it would fit into a growing trend of using archaeological artifacts and old data to fuel new scientific discoveries.

Researchers have already begun to explore the potential of unleashing artificial intelligence on old data sets, and some are pushing to digitize the once-stagnant back collections of natural history museums.

Everything old is new again — and the old stuff could be even older than we once thought.