Yes, I would guess they put
Shigella,
Entamoeba histolytica, Vibrio cholerae and many others. Life expectancy in dark age societies wasn't much different from that (45-55 yo) in great part to pathogens like these being relatively common in the water suply, in the abscense of modern sanitation. Combined with female deaths by child birth and widespread violence I would say TW got quite an accurate result.
Or are you surprised characters in a medieval simulation game are diyng before they turn 60 without the aid of modern medicine, water treatment and stable States?
edit:
If I didn't make myself clear, I for one completely support these natural premature deaths. It ain't old times if you can't catch diarhea and die out of the blue, in the middle of a campaign or chiling at your city. History has so many examples of leaders going out like that that makes it pretty hard to argue againts it. Please, devs, don't remove this feature, as it adds both realism and chance.