Table: Some Causes of Fever Based on Risk Factors - Merck Manuals Consumer Version

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Some Causes of Fever Based on Risk Factors

Some Causes of Fever Based on Risk Factors

Risk Factor	Cause
None (healthy)	Upper or lower respiratory tract infection Gastrointestinal infection Urinary tract infection Skin infection
Hospitalization	Infection related to a catheter inserted in a vein (IV catheter infection) Urinary tract infection, particularly in people with a urinary catheter Pneumonia, particularly in people on a ventilator Atelectasis (collapse of part of a lung due to an airway blockage, rather than an infection) Infection or a pocket of blood (hematoma) at the site of surgery Deep vein thrombosis or pulmonary embolism Diarrhea (due to Clostridioides difficile–induced colitis) Drugs Transfusion reaction Pressure sores
Travel to areas where an infection is common (endemic areas)	Malaria Viral hepatitis Disorders that cause diarrhea Typhoid fever Zika virus, chikungunya, Ebola virus, Japanese encephalitis, rabies, measles, and yellow fever Dengue fever Fungal infections such as coccidioidomycosis, blastomycosis, or histoplasmosis Rickettsial infections (such as African tick-bite fever and Mediterranean spotted fever)
Exposure to insects or animals that carry disease-causing organisms, called vectors (in the United States)	Ticks: Rickettsiosis, ehrlichiosis or anaplasmosis, Lyme disease, babesiosis, relapsing fever, or tularemia Mosquitoes: Encephalitis caused by arboviruses, malaria, or Zika virus infection Wild animals: Tularemia, rabies, or hantavirus infection Fleas: Plague Domestic animals: Brucellosis, cat-scratch disease, Q fever, or toxoplasmosis Birds: Psittacosis Reptiles: Salmonella infection Bats: Rabies or histoplasmosis
A weakened immune system (immunocompromise)	Viruses: Varicella-zoster virus infection or cytomegalovirus infection Bacteria: Infection due to pneumococci, meningococci, Staphylococcus aureus, Pseudomonas aeruginosa, Nocardia, or mycobacteria Fungi: Infection due to Candida, Aspergillus, Histoplasma, Coccidioides, microsporidia, Pneumocystis jirovecii, or fungi that cause mucormycosis Parasites: Infection due to Toxoplasma gondii, Strongyloides stercoralis, Cryptosporidium, or Cystoisospora belli
Drugs that can increase heat production	Amphetamines Cocaine Phencyclidine (PCP) Methylenedioxymethamphetamine (MDMA, or Ecstasy) Antipsychotic drugs Anesthetics
Drugs that can trigger fever	Beta-lactam antibiotics (such as penicillin) Sulfa drugs Phenytoin Carbamazepine Procainamide Quinidine Amphotericin B Interferons (drugs that are based on substances produced by the immune system and that help block the reproduction of viruses)