Merck Manual

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Some Causes of Fever Based on Risk Factors

Some Causes of Fever Based on Risk Factors

Risk Factor


None (healthy)

Upper or lower respiratory tract infection

Gastrointestinal infection

Bloodstream infection related to a catheter inserted in a vein (IV catheter infection)

Urinary tract infection, particularly in people with a urinary catheter

Infection or a pocket of blood (hematoma) at the site of surgery


Transfusion reaction

Travel to areas where an infection is common (endemic areas)

Disorders that cause diarrhea

Exposure to insects or animals that carry disease-causing organisms, called vectors (in the United States)

A weakened immune system (immunocompromise)

Drugs that can alter body temperature


Interferons (drugs that are based on substances produced by the immune system and that help block the reproduction of viruses)

Drugs that can trigger fever by a hypersensitivity reaction

Sulfa drugs





Amphotericin B