This kid was an 18 yr old cavalryman. He was captured Sept 22 and died Nov 17 after having been transferred at least twice to prison camps on the way from "near Knoxville" to Indianapolis.
There was an epidemic of "smallpox" about that time in the Indianapolis prison camp. "Smallpox" was not exactly a firm diagnosis in those times - the 8th Ga Inf was put into quarantine for "smallpox", but whatever the disease was, it wasn't smallpox as we know it.
I think stroke and injury are unlikely. Too young for stroke and injury would probably have been noted as such, so some kind of disease. Encephalitis, meningitis, "camp fever"??
They certainly didn't do an autopsy, so I wonder what the symptoms were that would lead to "congestion of brain" Headaches? Or.....?