My Great Grandfather was captured at Dandridge TN and went as a POW to Castle Thunder to Belle Isle to Andersonville to Savannah and then to Millen, before being exchanged in Nov 1864 from Savannah, I think in an "invalid prisoner" exchange.
After arrival at Andersonville he suffered from typhoid pneumonia and was nursed back to health by a friend from his cavalry troop, George Wall. Because he had some knowledge of pharmaceuticals from apprenticing with chemist/pharmacists in Philadelphia, he was assigned to work in the gangrene ward at Andersonville. Soon after he moved out from the general population to work on that ward, George Wall was carried out dead.
"After the cold of Belle Island and the confinement of the life there, the sun at Andersonville brought on my own misfortune. As we stood up in line one morning to be divided into squads I fell over on my face in a faint, and then and there laid down with the commencement of typhoid pneumonia. It seemed like a billet for the other world under the existing conditions – no hospital, no shelter, no food, no medicine, on the ground, inclement March and April ahead. Could conditions be more adverse?...
...I can recall no special suffering or distress from my own illness, except the misery of it all and the knowledge that I saw my comrade thought I was to be the first to respond to the hereafter call. I was spared. After three months I commenced to mend and get about. Having some knowledge of medicine, I had charge, with another prisoner, of some of the gangrene patients – not a very healthful occupation under the circumstances. George Wall had me transferred and he remained inside. I had not been out long – about July 1st – when poor George was carried out a corpse, having died away from me. It saddened my life, as we had been close "bunkies" ever since our capture in December – slept together, shared our small rations, comforted and cheered each other as best we could. He nursed me from March 10th, for three months, like a mother, cooking what little I required and nestling close to me in the long, cold nights, to keep me warm."
After he was exchanged, he was at Camp Comfort in Parole (Annapolis), MD but soon after arrival was given leave to return home to Philadelphia for about a month. He then returned to Annapolis until mustered out, I believe. On his return to Philadelphia, he may have continued to work for the pharmacists Bullock & Crenshaw as a clerk, then attended law school in 1867, passing the bar in 1869, and continued at Bullock & Crenshaw as an accountant and lawyer at least until 1881. When the pharmacists Smith & Kline were incorporated in 1888, he was listed as the Secretary of the Board. He continued in that role when, after an acquisition, it became Smith, Kline & French in 1891 (we now know it as the company Glaxo Smith Kline or GSK). He died in 1904. Based on letters with his wife and children, as well as newspaper articles, it appears he had medical issues throughout his life and often traveled to places that were supposed to be good for his health, both in the US and Europe. He died at home after a regular day of work and his Certificate of Death listed cause as myocarditis with a contributing factor of acute gastritis. He was 62. His wife, 6 years younger, lived till 1923, dying at the age of 74.