The Mustard gas could have weakened his gums - horrible stuff. I don't believe anybody did or has done a study of the links between Mustard gas exposure(however slight) and influenza deaths.
He married Betty Grable 1937 which did not last long div. 1939. But as you know she was very much the number one pin-up in WWII (US but Anglos as well) so that must have led to some difficult moments. He was probably the only US soldier not to have her photo pinned up.