Tags: Disease.
Fever of unknown origin (FUO) pyrexia of unknown origin (PUO) or febris e causa ignota (febris E.C.I.) refers to a condition in which the patient has an elevated temperature but despite investigations by a physician no explanation has been found.If the cause is found it usually is a diagnosis of exclusion that is by eliminating all possibilities until only one explanation remains and taking this as the correct one.