IL13 and myalgic encephalomeyelitis/chronic fatigue syndrome: Patients with stomach pain, bloating, and symptoms of an irritable bowel at pre-illness baseline, low levels of IL-13 and/or IL-5 at pre-illness baseline (previously discussed), and severe gastrointestinal symptoms at the time they contracted mononucleosis had a nearly 80% chance of developing severe ME/CFS six months following IM.