Fever of unknown origin
### What you need to know Fever of unknown origin (also known as fever of undetermined origin or pyrexia of unknown origin) is often a debilitating clinical syndrome. Patients with this syndrome present to medical practitioners across all levels of health care, including general practice, emergency department, and secondary care services, across all geographic areas.12345 There are limited epidemiological data on this syndrome, and no data related to primary care presentations. However, in two retrospective cohort studies from Japan and Italy, prevalence of fever of unknown origin in secondary care ranged from 1.9% to 2.9% in 9830 hospitalised patients.34 This article outlines the current diagnostic defining criteria, causes, and evaluation strategies, including newer diagnostic methods that have emerged over the past 20 years. We also outline management recommendations among immunocompetent adult patients with prolonged unexplained febrile conditions.6789 Fever of unknown origin is a
