Fever of unknown origin (FUO) refers to a condition in which the patient has an elevated temperature (fever) for which no cause can be found despite investigations by one or more qualified physicians.[1][2][3] If the cause is found, it is usually a diagnosis of exclusion, eliminating all possibilities until only the correct explanation remains.
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Mandell's Principles and Practices of Infection Diseases 6th Edition (2004) by Gerald L. Mandell MD, MACP, John E. Bennett MD, Raphael Dolin MD, ISBN0-443-06643-4 · Hardback · 4016 Pages Churchill Livingstone