Fever of unknown origin / suspected systemic infection

FUO is traditionally defined as fever ≥38.3°C on several occasions for ≥3 weeks with no diagnosis after appropriate evaluation. Modern context (Durack & Street 1991): the workup criterion is now ≥3 outpatient visits or ≥3 days inpatient (incl. ≥48h microbiology), and FUO is subdivided into classic, nosocomial, immunodeficient/neutropenic and HIV-associated categories — the immunocompromised categories are especially relevant to dental triage; some authors now favour a qualitative definition (persistent fever left undiagnosed despite considerable workup). A dental infection can occasionally be an occult cause of persistent fever, but SEPSIS should generally be excluded first if the patient looks unwell. KEY PRINCIPLE: fever + dental pain/swelling may be local infection, but fever + systemic deterioration = potential SEPSIS (time-critical). FIRST DECISION: treat in dental clinic vs refer urgently. This is a TRIAGE card.