Why Fever Occurs During the Flu: Immune Mechanism Explained

Fever is a regulated host defense, not merely a symptom. During influenza infection:

1. Immune cells (macrophages, dendritic cells) detect viral components → release pyrogenic cytokines (IL-1β, TNF-α, IL-6).
2. Cytokines act on the hypothalamic preoptic area → raise the thermostatic set point.
3. Body generates heat (shivering, vasoconstriction, ↑ metabolic rate) to reach new set point.

Benefits of Fever

• Enhanced leukocyte function: Neutrophil chemotaxis, phagocytosis, and T-cell proliferation improve at 38–40°C.
• Pathogen inhibition: Many viruses replicate poorly at elevated temperatures.
• Acute-phase response: Liver produces antimicrobial proteins (CRP, fibrinogen).

Antipyretics (acetaminophen, ibuprofen) improve comfort but may slightly prolong viral shedding. Use judiciously; focus on hydration and monitoring for complications.