It's not speculation, jorge. The first documentaries, created by the US Military, after the liberation of the camps, state quite clearly that the camps were infested with typhus, and that most of the inmates had it, and that the corpses were of inmates who died from it. They discuss the measures taken to battle it, and bring in massive quantities of medical supplies and vast numbers of medical personnel, food, potable water, etc., to address the problem.
POWs were generally kept in Germany, where conditions didn't deteriorate to nearly the same degree till after the actual invasion, and then they were quickly freed.
