Recent Advances in the Study of Q Fever Epidemiology, Diagnosis and Management

Q fever is a worldwide zoonotic infection with an epidemiological pattern consisting of sporadic cases, endemic situations and outbreaks of unsuspected magnitude, as occurred in Holland. This event highlighted the fact that the term "chronic Q fever" is misleading and should be avoided. Here, we review recent advances in the understanding and management of this disease. There have been clonal outbreaks of confirmed "geotypes," such as the outbreaks in French Guiana, where a very high incidence was restricted to one city, with a specific clinical expression, an unusual serological response and a putative common reservoir. The advent of positron emission tomography has improved the diagnosis of endocarditis, vascular and osteoarticular infections. Molecular tests, including fluorescent in situ hybridization, may be included in the diagnostic strategy using the new criteria for endocarditis, vascular and osteoarticular infections. Q fever during pregnancy is challenging because pregnant women are less symptomatic, but infection is associated with a poor fetal outcome, including malformations that are preventable by antibiotics. Male patients over 40 years old with a valvulopathy are at the highest risk for progression to endocarditis. Antibiotic prophylaxis prevents endocarditis in 100% of at-risk patients. Finally, IgG anticardiolipin antibodies, part of the auto-immune response during acute Q fever, were recently added to the risk factors for endocarditis, due to their ability to promote acute valvular lesions and endocarditis.