Most febrile illnesses are due to common infections and are relatively easy to diagnose. in certain instances, however, it is difficult to establish the cause of a fever. in these instances, the elevation in temperature is referred to as a fever of unknown origin (fuo). what is a common cause of fuo?

The fever of unknown origin, or the FUO can be defined as the condition when the body temperature of a person is at 101 degree Fahrenheit for at least a period of the three weeks without any observable underlying cause. The most common causes of the FUO includes, infections (such as Lyme disease, tuberculosis), malignancy (such as leukemia), inflammation (such as inflammatory bowel disease), and alcohol or drug abuse.