Final answer:
FUO is defined as an elevated body temperature in a random pattern that has persisted for at least 3 weeks. It is a chronic disease that usually manifests as acute febrile illness with recurring flu-like signs and symptoms.
Step-by-step explanation:
FUO (Fever of Unknown Origin) is defined as an elevated body temperature in a random pattern that has persisted for at least 3 weeks. It is a chronic disease that usually manifests as acute febrile illness with recurring flu-like signs and symptoms. The average normal body temperature is usually given as 37.0°C (98.6°F), and variations in this temperature can indicate a medical condition such as a fever, an infection, a tumor, or circulatory problems.