Q fever

Q fever is an infectious zoonosis caused by Coxiella burnetii ^[1][2]. The organism is described as an obligate or strict intracellular, Gram-negative bacterium with a high infection capacity, and it proliferates in an acidified intracellular compartment ^[1][2]. The sources also note antigenic phase variation linked to changes in membrane lipopolysaccharide complexity ^[1].

The sources describe two broad clinical presentations: an acute form, which is reported as more frequent and often asymptomatic, and a persistent focalized infection that occurs in about 4 to 5% of patients and is generally associated with poor evolution ^[1]. Another source notes that the clinical presentation depends on the virulence of the infecting strain and on patient-specific risk factors, and that persistent infection cannot exist without a focus of infection ^[2]. Infections are often subclinical, but severe and life-threatening complications may occur, and long-term sequelae can follow persistent infection ^[3]. More granular symptom-level detail is not yet available from the provided sources ^[1][2][3].

Q fever is reported worldwide, with variable geographical distribution and epidemiological patterns that may include endemic, hyperendemic, and large epidemic outbreak settings ^[1][2]. One source notes a Scottish outbreak and another states that the organism has a worldwide distribution with the notable exception of New Zealand ^[3]. The disease is said to affect people in rural areas who are in contact with animals, and it is described as rarely reported despite its ubiquity, suggesting possible underdiagnosis or under-reporting ^[1][3].

The most common human transmission route described in the sources is inhalation of aerosols containing the pathogen ^[1]. The aerosol risk is emphasized particularly for material formed from placental derivatives ^[1]. The organism’s host range includes arthropods, birds, and a diverse range of mammals, including livestock and companion animals, and these animals are identified as principal reservoirs alongside ticks ^[2][1].

The sources most clearly identify people in rural areas who are in contact with animals as a key affected group ^[1]. Occupational or exposure-related risk is also suggested for people working with animals or handling birth products ^[1]. Beyond these exposure-linked groups, the provided material does not supply enough source-backed detail to define additional high-risk populations with confidence ^[1][2].

The provided sources do not give a complete prevention guideline or formal control package ^[1][2][3]. They do indicate that exposure minimization measures should be undertaken for people working with animals or handling birth products, which is consistent with the aerosol exposure described in the sources ^[1]. Source-backed detail on vaccination, post-exposure measures, or specific occupational protocols is not yet available ^[1].

In surveillance terms, Q fever should be interpreted as a zoonotic bacterial infection with a wide animal reservoir and a transmission pattern dominated by aerosol exposure, especially around animal birth material ^[1][2]. The literature provided highlights variable geography, outbreak potential, and under-reporting, so apparent rarity should not be taken as evidence of absence ^[3]. The sources also emphasize that persistent focalized infection represents a distinct clinical pattern and that no persistent infection can exist without a focus, which may be relevant when interpreting prolonged or relapsing cases ^[2].

1. 1 España PP et al. Q Fever (Coxiella Burnetii). Semin Respir Crit Care Med. 2020 Aug. PMID: 32629489. doi: 10.1055/s-0040-1710594. PubMed: https://pubmed.ncbi.nlm.nih.gov/32629489/
2. 2 Eldin C et al. From Q Fever to Coxiella burnetii Infection: a Paradigm Change. Clin Microbiol Rev. 2017 Jan. PMID: 27856520. doi: 10.1128/CMR.00045-16. PubMed: https://pubmed.ncbi.nlm.nih.gov/27856520/
3. 3 Cutler SJ et al. Q fever. J Infect. 2007 Apr. PMID: 17147957. doi: 10.1016/j.jinf.2006.10.048. PubMed: https://pubmed.ncbi.nlm.nih.gov/17147957/
4. 4 Fevers. Herbs in the Treatment of Children. 2003. doi: 10.1016/b978-0-443-07163-8.50019-8. DOI: https://doi.org/10.1016/b978-0-443-07163-8.50019-8
5. 5 Fevers. Crocologia – A Detailed Study of Saffron, the King of Plants. 2020. doi: 10.1163/9789004435292_024. DOI: https://doi.org/10.1163/9789004435292_024
6. 6 Typhoid Fever (Paratyphoid Fever, Enteric Fever). Netter's Gastroenterology. 2010. doi: 10.1016/b978-1-4377-0121-0.50175-6. DOI: https://doi.org/10.1016/b978-1-4377-0121-0.50175-6

ICD-10

ICD-11

Total cases

18K

Peak month

2019-01

Coverage

8 reporting countries · 2000-01-01 → 2026-06-20