Q Fever Differential Diagnoses

Updated: Feb 01, 2023
  • Author: Kerry O Cleveland, MD; Chief Editor: John L Brusch, MD, FACP  more...
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Diagnostic Considerations

Q fever is difficult to diagnose, primarily because physicians tend not to think of it in the differential diagnosis. Failure to consider the diagnosis and failure to maintain an epidemiologic approach with any cluster of clinical presentations, particularly atypical pneumonia or hepatitis, eliminates any possibility of making the diagnosis.

The Centers for Disease Control and Prevention (CDC) recommends that physicians evaluate travelers, particularly military personnel and civilian contractors, for Q fever if they present with febrile illness, pneumonia, or hepatitis. [16] Confirmed and suspected cases should be reported to local health departments.

Consider the possibility of tick-borne illnesses in all patients with febrile illnesses. Also, exposures to animals, animal by-products, and parturient animals are risk factors. In patients with culture-negative endocarditis, consider infection with C burnetii.

In this age of concern for terrorism with biologic agents, Q fever is on the list of possible agents. The initial diagnosis might be delayed by the fact that it is so uncommon in most locations. [8]

Other conditions that are considered in the differential diagnosis include the following:

  • Acute interstitial pneumonitis

  • Arbovirus encephalitis

  • Atypical pneumonia caused by viruses, Chlamydia species, or Mycoplasma

  • Bacterial and infective endocarditis, bacterial pericarditis

  • Brucellosis

  • Chlamydial infections

  • Connective-tissue diseases

  • Hepatitis: Drug-induced, granulomatous, viral

  • Ebstein-Barr virus

  • Leptospirosis

  • Mediterranean fever

  • Meningoencephalitis, aseptic meningitis

  • Osteomyelitis or osteoarticular Infection

  • Southern tick-associated rash illness (STARI)

  • Spontaneous abortion, placentitis

  • Tick-borne diseases (Colorado tick-borne diseases, ehrlichiosis, Lyme disease, relapsing fever, Rocky Mountain spotted fever, tularemia)

  • TORCH syndrome (toxoplasmosis, rubella, cytomegalovirus, and herpes simplex infections)

  • Vascular graft infections

  • Visceral leishmaniasis

Differential Diagnoses