According to the Civil War Database, Private Edmond C. Maxwell of Company D of the 28th Alabama Infantry died of disease while a POW on August 14, 1864 at Rock Island, Illinois. While he did die on August 14, 1864 at Rock Island I don't believe he died of disease.

Private E. C. M-------, Company D 28th Alabama Infantry, a prisoner of war at Rock Island, Illinois, was killed by a fellow prisoner, August 14, 1864 by a blow on the right temporal region with a board. Death was almost instantaneous. At the autopsy, it was found that the skull was remarkably thin and that a nearly vertical fissure extended through the squamous portion of the temporal, the great wing of the sphenoid and nearly to the median line of the frontal bone, bifurcating an inch from its termination. The right orbital plate of the frontal, which was extremely thin, was fissured either by contre coup, or by the impulse communicated through the cerebral substance. There was diastasis of the squamo-sphenoid suture. Large branches of the meningeal arteries were ruptured and death resulted, probably from hemorrhage in the cavity of the cranium. But the condition of the brain and its membranes and the extent of the intracranial bleeding, were not reported. The specimen is delineated in the adjacent wood-cut Fig. 17. By an inadvertence of the engraver in copying the photograph, the specimen appears reversed, and represents a fracture of the left instead of the right side. Spec. 2862.