A Comprehensive Review of the Mechanisms of Human Q Fever: Pathogenesis and Pathophysiology

Coxiella burnetii infection has a worldwide distribution, although the incidence and clinical manifestations vary between and within countries. There are the following four basic forms: asymptomatic infection, acute Q fever, chronic Q fever, and post-Q fever fatigue syndrome. The aim of this review is to provide a comprehensive overview of the important aspects of its pathogenesis and pathophysiology. First, we provide a brief update of the taxonomic aspects, basic structures, and genotypes of C. burnetii necessary for the proper interpretation of the following sections. Routes of infection, different stages of pathogenesis (respiratory entry of C. burnetii; penetration into alveolar macrophages, life cycle, and effects; systemic dissemination), and innate, acquired humoral and cell-mediated immune responses in different forms of infection are described in detail. The pathophysiology and clinical manifestations of Q fever, such as the main mechanisms of injury, in isolation and in combination, are reviewed. The clinical and biological manifestations of the two main forms of Q fever (acute and chronic) are outlined, with a brief definition and mention of the mechanisms of post-Q fever fatigue syndrome.