Many chronic illnesses can cause belly (abdominal) pain. These illnesses include sickle cell disease, diabetes, inflammatory bowel disease (IBD), and cystic fibrosis.

Sudden (acute) illnesses, such as strep throat and influenza (flu), can cause belly pain when the glands in the belly become swollen or inflamed. These glands are called lymph nodes. When they are inflamed, it's called mesenteric adenitis.