Fever of unknown origin (peds)

This page is for pediatric patients. For adult patients, see: fever of unknown origin


  • Prolonged fever of unknown origin without identified cause generally has favorable prognosis.

Clinical Features

  • Original definition[1]
    • Fever >38.3 C on several occasions
    • Lasting for at least 3 weeks
    • No clear diagnosis after 1 week inpatient workup
  • Newer definition[2] - "Prolonged fever" with:
    • 3 outpatient visits without identifying a cause or
    • 3 inpatient days without identifying a cause or
    • 1 week of “intelligent and invasive” ambulatory investigation

Differential Diagnosis


  • Clinical (preliminary) diagnosis


  • Treat underlying cause (once identified)
  • Empiric treatment generally not recommended


  • Frequently admitted for workup

See Also


  1. Kaya A, Ergul N, Kaya SY, et al. The management and the diagnosis of fever of unknown origin. Expert Rev Anti Infect Ther. 2013 Aug;11(8):805-15.
  2. Durack DT, Street AC. Fever of unknown origin--reexamined and redefined. Curr Clin Top Infect Dis. 1991;11:35-51.