Infectious and non-infectious causes of fever

This topic has come up a couple of times in the CICM past papers, notably in  Question 9 from the second paper of 2009 and in Question 1 from the second paper of 2002. Each time the college examiner failed to distinguish between hyperthermia and fever, which are distinct entities. To borrow a turn of phrase from Still (1979), fever is a regulated increase in body temperature associated with an increased hypothalamic temperature setpoint and thermopreferendum (the behavioural preference for an environmental temperature), whereas in hyperthermia the body temperature is elevated above this preferred homeostatic set point. As such causes of elevated body temperature shoud be classified in terms of whether the temperature is elevated because of the body's thermoregulatory mechanisms, or in spite of them.  

However, for the purpose of answering questions on this topic, the trainees were not expected to discriminate between hyperthermia and fever. As such Paul Marik's excellent article on fever remains a definitive resource for the person trying to generate a broad range of differentials. The need to generate such a range has come up several times in the CICM written papers.  Given the broad range of things that can get infected (or non-infectiously inflamed) one can hardly call any list a "definitive" list. However, somewhere in one's cognitive arsenal one ought to have a table which looks like this, covering the major categories.

Differential Diagnosis of Fever in the ICU Patient

Infectious causes (i.e. sources)

Noninfectious causes

  • Airway
    • Pharyngitis
    • Sinusitis (eg. NG-tube associated)
    • Dental infection
  • Respiratory system
    • Pneumonia, bronchitis
    • VAP
  • Circulatory system
    • CVC-associated bloodstream infections
    • Endocarditis, pericarditis, myocarditis
    • Vascular graft infection
    • Infected peripheral cannula
    • Aortitis
    • Mediastinitis
  • Central nervous system
    • Meningitis
    • Encephalitis
    • Epidural abscess
  • Endocrine system
    • Prostatitis
  • Renal/urinary tract
    • Nephritis / pyelonephritis
    • Infected ureteric calculus
    • Cystitis
    • UTI due to IDC
  • Gastrointestinal tract
    • Oeseophagitis
    • Pancreatitis
    • Bowel perforation, ischaemia etc
    • Diverticulitis
    • Perianal or psoas abscess
    • C.difficile colitis
  • Haematological causes
    • Malaria
  • Integument (bones, ligaments, soft tissues)
    • Osteomyelitis, discitis
    • Necrotising fasciitis
    • Cellulitis
  • Vascular
    • Cerebral infarction/hemorrhage
    • Myocardial infarction
    • Ischemic bowel
    • Subarachnoid hemorrhage
    • Fat emboli
    • Deep venous thrombosis/PE
    • Phlebitis/thrombophlebitis
  • Neoplastic
    • Lymphoma-associated fever
    • Renal cell carcinoma
    • Tumour lysis syndrome
  • Drug-induced
    • Alcohol/drug withdrawal
    • Drug fever
  • Idiopathic inflammatory
    • Postoperative fever (48 h postoperative)
    • Acalculous cholecystitis
    • Pancreatitis
    • Aspiration pneumonitis
    • ARDS
    • Gout/pseudogout
    • IV contrast reaction
    • GI bleed
  • Autoimmune
    • Posttransfusion fever
    • Transplant rejection
    • Vasculitis
    • Haemolytic anaemia
  • Traumatic/environmental
    • Haematoma degradation
    • Decubitus ulcers
    • Heat stroke
  • Endocrine
    • Adrenal insufficiency
    • Thyrotoxicosis
    • Thyroiditis (Hashimoto)
    • Ovulation


Bota, Daliana Peres, et al. "Body temperature alterations in the critically ill."Intensive care medicine 30.5 (2004): 811-816.

Marik, Paul E. "Fever in the ICU." Chest Journal 117.3 (2000): 855-869.

Efstathiou, Stamatis P., et al. "Fever of unknown origin: discrimination between infectious and non-infectious causes." European journal of internal medicine21.2 (2010): 137-143.

Stitt, John T. "Fever versus hyperthermia." Federation proceedings. Vol. 38. No. 1. 1979.