Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Microbiology and epidemiology of Q fever

Didier Raoult, MD, PhD
Section Editor
Daniel J Sexton, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Q fever is a zoonotic infection caused by the pathogen Coxiella burnetii, which can cause acute or chronic disease with protean manifestations [1]. The designation Q fever (from Query) was made in 1935 following an outbreak of febrile illness in an abattoir in Queensland, Australia.

The microbiology and epidemiology of Q fever will be reviewed here. The clinical features, diagnosis, and treatment of Q fever are discussed separately. (See "Clinical manifestations and diagnosis of Q fever" and "Q fever endocarditis".)


C. burnetii is a short, pleomorphic rod that is a strict intracellular bacterium. While previously designated as a Rickettsia, C. burnetii has been re-classified as a Proteobacteria, which is closer to Legionella and Francisella [2]. C. burnetii can be cultivated in embryonated eggs, laboratory animals, and in vitro cell culture systems [3,4]. It can also be cultured in axenic (host cell-free) media [4,5].

In mammals, the usual host cell of C. burnetii is the macrophage, which is unable to kill the bacterium. C. burnetii lives and multiplies in a single, large, acidic vacuole, which results from the fusion of cell lysosomes [6]. In addition, a sporulation-like process protects the organism from the external environment, where it can survive for long periods of time.

An important characteristic of C. burnetii is its antigenic variation, called "phase variation". When C. burnetii express phase I antigen it is highly infectious and a single bacterium is sufficient to infect a human. This is the form that is isolated from animals or humans. After subculturing C. burnetii in cells or embryonated eggs, modification of its lipopolysaccharide (LPS) capsule results in an antigenic shift to the phase II form, which is not infectious. This antigenic shift can be measured and forms the basis for differentiating acute from chronic Q fever [1].

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:

Subscribers log in here

Literature review current through: Nov 2017. | This topic last updated: Nov 20, 2017.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2017 UpToDate, Inc.
  1. Raoult D, Marrie T. Q fever. Clin Infect Dis 1995; 20:489.
  2. Stein A, Saunders NA, Taylor AG, Raoult D. Phylogenic homogeneity of Coxiella burnetii strains as determinated by 16S ribosomal RNA sequencing. FEMS Microbiol Lett 1993; 113:339.
  3. Raoult D. Q fever: still a query after all these years. J Med Microbiol 1996; 44:77.
  4. Omsland A, Cockrell DC, Howe D, et al. Host cell-free growth of the Q fever bacterium Coxiella burnetii. Proc Natl Acad Sci U S A 2009; 106:4430.
  5. Singh S, Kowalczewska M, Edouard S, et al. Cell extract-containing medium for culture of intracellular fastidious bacteria. J Clin Microbiol 2013; 51:2599.
  6. Maurin M, Benoliel AM, Bongrand P, Raoult D. Phagolysosomal alkalinization and the bactericidal effect of antibiotics: the Coxiella burnetii paradigm. J Infect Dis 1992; 166:1097.
  7. Hackert VH, van der Hoek W, Dukers-Muijrers N, et al. Q fever: single-point source outbreak with high attack rates and massive numbers of undetected infections across an entire region. Clin Infect Dis 2012; 55:1591.
  8. Frankel D, Richet H, Renvoisé A, Raoult D. Q fever in France, 1985-2009. Emerg Infect Dis 2011; 17:350.
  9. Tissot Dupont H, Raoult D, Brouqui P, et al. Epidemiologic features and clinical presentation of acute Q fever in hospitalized patients: 323 French cases. Am J Med 1992; 93:427.
  10. Cilla G, Montes M, Perez-Trallero E. Q fever in the Netherlands - what matters is seriousness of disease rather than quantity. Euro Surveill 2008; 13.
  11. Edouard S, Mahamat A, Demar M, et al. Comparison between emerging Q fever in French Guiana and endemic Q fever in Marseille, France. Am J Trop Med Hyg 2014; 90:915.
  12. Epelboin L, Chesnais C, Boullé C, et al. Q fever pneumonia in French Guiana: prevalence, risk factors, and prognostic score. Clin Infect Dis 2012; 55:67.
  13. Eldin C, Mahamat A, Demar M, et al. Q fever in French Guiana. Am J Trop Med Hyg 2014; 91:771.
  14. Anderson AD, Smoak B, Shuping E, et al. Q fever and the US military. Emerg Infect Dis 2005; 11:1320.
  15. Leung-Shea C, Danaher PJ. Q fever in members of the United States armed forces returning from Iraq. Clin Infect Dis 2006; 43:e77.
  16. Stein A, Raoult D. Pigeon pneumonia in provence: a bird-borne Q fever outbreak. Clin Infect Dis 1999; 29:617.
  17. Gardon J, Héraud JM, Laventure S, et al. Suburban transmission of Q fever in French Guiana: evidence of a wild reservoir. J Infect Dis 2001; 184:278.
  18. Eldin C, Mahamat A, Djossou F, Raoult D. Rainfall and sloth births in may, Q fever in July, Cayenne, French Guiana. Am J Trop Med Hyg 2015; 92:979.
  19. Ben Amara A, Ghigo E, Le Priol Y, et al. Coxiella burnetii, the agent of Q fever, replicates within trophoblasts and induces a unique transcriptional response. PLoS One 2010; 5:e15315.
  20. Racult D, Stein A. Q fever during pregnancy--a risk for women, fetuses, and obstetricians. N Engl J Med 1994; 330:371.
  21. Pantanowitz L, Telford SR, Cannon ME. Tick-borne diseases in transfusion medicine. Transfus Med 2002; 12:85.
  22. Signs KA, Stobierski MG, Gandhi TN. Q fever cluster among raw milk drinkers in Michigan, 2011. Clin Infect Dis 2012; 55:1387.
  23. Amitai Z, Bromberg M, Bernstein M, et al. A large Q fever outbreak in an urban school in central Israel. Clin Infect Dis 2010; 50:1433.
  24. Osorio S, Sarriá C, González-Ruano P, et al. Nosocomial transmission of Q fever. J Hosp Infect 2003; 54:162.
  25. Milazzo A, Hall R, Storm PA, et al. Sexually transmitted Q fever. Clin Infect Dis 2001; 33:399.
  26. Whitney EA, Massung RF, Candee AJ, et al. Seroepidemiologic and occupational risk survey for Coxiella burnetii antibodies among US veterinarians. Clin Infect Dis 2009; 48:550.
  27. Centers for Disease Control and Prevention (CDC). Notes from the field: Q fever outbreak associated with goat farms--Washington and Montana, 2011. MMWR Morb Mortal Wkly Rep 2011; 60:1393.
  28. Wade AJ, Cheng AC, Athan E, et al. Q fever outbreak at a cosmetics supply factory. Clin Infect Dis 2006; 42:e50.
  29. Raoult D, Tissot-Dupont H, Foucault C, et al. Q fever 1985-1998. Clinical and epidemiologic features of 1,383 infections. Medicine (Baltimore) 2000; 79:109.
  30. Raoult D, Marrie T, Mege J. Natural history and pathophysiology of Q fever. Lancet Infect Dis 2005; 5:219.
  31. Raoult D, Levy PY, Dupont HT, et al. Q fever and HIV infection. AIDS 1993; 7:81.
  32. Prabhu M, Nicholson WL, Roche AJ, et al. Q fever, spotted fever group, and typhus group rickettsioses among hospitalized febrile patients in northern Tanzania. Clin Infect Dis 2011; 53:e8.
  33. Million M, Roblot F, Carles D, et al. Reevaluation of the risk of fetal death and malformation after Q Fever. Clin Infect Dis 2014; 59:256.
  34. Breteler JK, Oudhoff JP, Munster JM, et al. Risks, trust and knowledge: determinants of pregnant women's decisions regarding participation in a future Q fever screening and treatment program during a large epidemic in The Netherlands. Prenat Diagn 2011; 31:814.
  35. Munster JM, Leenders AC, van der Hoek W, et al. Cost-effectiveness of a screening strategy for Q fever among pregnant women in risk areas: a clustered randomized controlled trial. BMC Womens Health 2010; 10:32.
  36. Denman J, Woods M. Acute Q fever in pregnancy: report and literature review. Intern Med J 2009; 39:479.
  37. Carcopino X, Raoult D, Bretelle F, et al. Q Fever during pregnancy: a cause of poor fetal and maternal outcome. Ann N Y Acad Sci 2009; 1166:79.
  38. Raoult D, Fenollar F, Stein A. Q fever during pregnancy: diagnosis, treatment, and follow-up. Arch Intern Med 2002; 162:701.
  39. Centers for Disease Control and Prevention (CDC), Jajosky RA, Hall PA, et al. Summary of notifiable diseases--United States, 2004. MMWR Morb Mortal Wkly Rep 2006; 53:1.
  40. Karakousis PC, Trucksis M, Dumler JS. Chronic Q fever in the United States. J Clin Microbiol 2006; 44:2283.
  41. Raoult D. Reemergence of Q fever after 11 September 2001. Clin Infect Dis 2009; 48:558.