According to the Mayo Clinic, Crohn's disease is marked by a chronic inflammation of the digestive tract. We still don't know exactly what causes the condition, but it may be the result of an overactive immune system. Symptoms of Crohn's include digestive issues such as diarrhea and bloody stool, as well as other physical problems like cramping and abdominal pain, fever, and general weakness.
These symptoms usually come on earlier in life, as, according to the Mayo Clinic, most cases are diagnosed before the age of 30. While people living with Crohn's may experience symptoms over a long period of time, there are often periods of remission.
When comparing what we know about Crohn's today with the reported illness that Alfred the Great suffered from, it's not hard to see why Craig and others suspect the king may have been living with Crohn's. Not only do many of his symptoms line up, but the onset of his illness also matches, as does the fact that Alfred likely enjoyed periods where he didn't experience symptoms..
A last important clue lies in Alfred's lineage. It's not known exactly why people develop Crohn's, but there is evidence to suggest that those who have relatives with the disease are more likely to develop it themselves. King Eadred, a grandson of Alfred, ruled England in the mid 10th century. Like his grandfather, he suffered from an illness of the stomach, which he is presumed to have died of when he was in his early 30s (via Historic UK).
We'll never know for sure what illness Alfred the Great, or his fictional counterpart on Vikings, suffered from. However, given the evidence at hand, it appears that Crohn's disease is the most likely culprit.
