RT Book, Section A1 Steele, Russell W. A2 Kline, Mark W. SR Print(0) ID 1182933659 T1 Fever of Unknown Origin T2 Rudolph's Pediatrics, 23e YR 2018 FD 2018 PB McGraw-Hill Education PP New York, NY SN 9781259588594 LK accesspediatrics.mhmedical.com/content.aspx?aid=1182933659 RD 2024/10/13 AB The definition of fever of unknown origin (FUO) in an immunologically normal host requires an oral or rectal temperature ≥ 38.0°C (100.4°F) at least twice a week for more than 3 weeks and a noncontributory history and physical examination. FUO should not be confused with fevers of shorter duration variously termed “fever without localizing signs” (< 7 days) and “fever without source” (FWS) (7–14 days). Management of patients with comorbidity factors such as acquired or congenital immunodeficiency, neutropenia, and occurrence of fever during prolonged hospital stays is not considered in the following discussion since the differential diagnosis and evaluation of these patients vary considerably.