febrile

Febrile, from Latin febris meaning fever, is a state of having a fever or warmth associated with an elevated body temperature. In clinical terms, fever is typically defined as a measured body temperature above the normal range, commonly 38°C (100.4°F) taken orally, 38.0°C (100.4°F) rectally, or equivalent. The febrile response is regulated by the hypothalamus and is driven by pyrogens—exogenous like bacterial toxins, and endogenous cytokines such as IL-1, IL-6, and TNF-α—that raise the hypothalamic set point. Fever is a symptom rather than a disease, and can accompany many conditions.

Most febrile illnesses are infectious (viral or bacterial), but fever can also occur with inflammatory diseases, autoimmune disorders, malignancies, drug reactions, or heat-related illnesses. In children, febrile illness is common; febrile seizures may occur in a subset. In older adults or the immunocompromised, fever may present without typical symptoms.

Evaluation seeks to identify the underlying cause and may involve history, physical examination, and selective laboratory tests. Red flags include persistent fever despite therapy, fever with severe illness, altered mental status, immunocompromise, or a focal finding suggesting a specific infection. Management focuses on treating the underlying cause when possible, and symptomatic relief with antipyretics such as paracetamol (acetaminophen) or ibuprofen, while avoiding aspirin in young children. Adequate hydration and monitoring are advised.

Prognosis depends on the underlying condition; most febrile illnesses are self-limited. Febrile presentations require careful assessment in vulnerable groups, and recurrent or prolonged fever warrants medical evaluation.