Virginia --

George Levy's recent book, To Die in Chicago: Confederate Prisoners at Camp Douglas, 1862-1865 tells the story of the thousands who passed through this prison.

http://www.civilwarmed.org/shop/product.htm?id=2256

The large majority of the thousands held there refused to take the oath of allegiance, so that's not the exact cause of death for these two men.

You can order copies of millitary service files (including prisoner of war records) here --