Q Fever

Aka: Q Fever, Coxiella Burnetii, Nine Mile Fever

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II. Pathophysiology

  1. Coxiella Burnetii
    1. Gram Negative, small coccobacilli
    2. Obligate Intracellular Bacteria
      1. Similar to Rickettsiae, but has been reclassified to the family Coxiellaceae
      2. C. Burnetii uses host ATP within host cell to grow and divide
    3. Spore forming (Endospore)
      1. C. Burnetii can form an endospore (similar to Clostridium species)
      2. Endospore form is resistant to heat and dry air
      3. Endospore form allows organism to survive outside host cells for extended periods
      4. Organism lies dormant in endospore form (must be intracellular to grow and divide)
  2. Transmission
    1. Exposure to farm animals (esp. cattle, goats, sheep)
    2. Typically transmitted via aerosolized C. Burnetii spores
      1. Animal feces
      2. Dried cow placenta
      3. Dried tick feces on hides
      4. Contaminated soil
    3. May also be transmitted by the ingestion of unpasteurized milk
      1. To be destroyed, Coxiella Burnetii endospores must be heated to at least 60 C
    4. Tick Borne Illness transmission occurs, but is rare
  3. Incubation
    1. Three weeks (ranges from 9-40 days)

III. Symptoms

  1. Flu-like symptoms
    1. Fever
    2. Malaise
    3. Headache
    4. Myalgias
    5. Arthralgias
  2. Respiratory symptoms (mild, Atypical Pneumonia similar to Mycoplasma pneumonia)
    1. Dry cough
    2. Pleuritic Chest Pain
  3. Gastrointestinal symptoms
    1. Nausea
    2. Vomiting
    3. Diarrhea

IV. Labs

  1. Blood Cultures are typically negative
  2. Coxiella Burnetii PCR
  3. Serology (IFA)

V. Management: Acute Infections

  1. Precautions
    1. See other references for chronic infections, endocarditis or comorbid endocarditis risk
  2. Non-Pregnant Adults and Children age >8 years
    1. Doxycycline 2.2 mg/kg up to 100 mg orally twice daily for 2 weeks
  3. Pregnancy
    1. Trimethoprim-Sulfamethoxazole DS 1 orally twice daily
      1. Continued until later third trimester to prevent Preterm Labor
      2. Discontinued prior to delivery to prevent Kernicterus
  4. Children age <8 years
    1. Trimethoprim-Sulfamethoxazole for 14 days (see link for dosing)

VI. Complications

  1. Atypical Pneumonia
  2. Acute Respiratory Distress Syndrome (ARDS)
  3. Granulomatous Hepatitis
  4. Vascular Infections
  5. Bacterial Endocarditis (2% of cases)
    1. Often culture negative
    2. Melenotte (2019) Clin Infect Dis 69(11):1987-1995 +PMID: 30785186 [PubMed]
  6. Chronic Infection (<5% of cases)
    1. Kampschreur (2015) Emerg Infect Dis 21(7):1183-8 +PMID: 26277798 [PubMed]

VII. Prognosis

  1. Most cases are mild and resolve spontaneously within 2 weeks
  2. However, Bacterial Endocarditis and chronic infections may complicate infection

VIII. Resources

  1. Q Fever (Wikipedia)
    1. https://en.wikipedia.org/wiki/Q_fever

IX. References

  1. (2025) Sanford Guide, accessed on IOS 2/14/2025
  2. Black, Martin, DeVos (2018) Crit Dec Emerg Med 32(8): 3-12
  3. Nordurft-Froman and DeVos (2022) Crit Dec Emerg Med 36(4): 4-15

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