What are the worst things that can grow on the human body? What flesh diseases are treatable? This list of physical diseases highlights some of the terrible things that affect the human body and what can be done to treat them. In some cases, there is no cure for these conditions, only options for treatment. Fortunately, many of these conditions have long since been suppressed into remission and are not as often seen in most parts of the world, though many of these infectious diseases do still exist.