A gastrointestinal system infectious disease that involves inflammation and infection of the appendix caused by the blockage of the lumen with a small, hard piece of stool, a foreign body or worms. Mucus backs up in the appendiceal lumen, causing bacteria that live inside the appendix to multiply. The infection has_symptom pain, in the upper abdomen initially and later in the lower abdomen, has_symptom nausea, has_symptom vomiting and has_symptom fever.