Global epidemiology and molecular typing of Coxiella burnetii: A systematic review of Q fever in humans and animals

This systematic review, conducted according to PRISMA guidelines, provides a comprehensive synthesis of epidemiological data on Coxiella burnetii, the causative agent of Q fever, in humans and animals worldwide. A total of 1321 publications were identified, of which 166 met the inclusion criteria. Q fever, first described in 1937 in Australian abattoir workers, remains a globally distributed zoonosis, with domestic ruminants (sheep, goats, cattle) serving as the primary reservoirs and sources of human infection. Transmission occurs mainly via inhalation of contaminated aerosols, particularly during parturition or abortion events. The pathogen is a strict intracellular bacterium with a small genome (∼2 Mb) and plasmid diversity that contributes to strain variation. Laboratory diagnosis relies primarily on serology (IFA as gold standard) and PCR for early detection, while cultivation is restricted to BSL-3 facilities due to biosafety concerns. Molecular epidemiology has progressed with typing methods such as Multispacer Sequence Typing (MST), Multiple-Locus Variable number tandem repeat Analysis (MLVA), and Whole Genome Sequencing (WGS). MST is widely used due to its reproducibility and application to clinical and environmental samples, though MLVA and WGS provide higher discriminatory power. Genotyping has revealed significant host- and region-specific diversity, with some lineages, such as MST17 in French Guiana, associated with severe disease. Geographically, Q fever shows marked heterogeneity. In Europe, sporadic cases coexist with large outbreaks, exemplified by the Netherlands epidemic (2007–2010) with > 4000 confirmed human cases linked to goat farms. France, Germany, Spain, and Italy also report endemicity, often with regionally distinct genotypes. In Africa, prevalence varies widely, reaching up to 32 % in Egypt and > 70 % in camels in Algeria, though surveillance is limited. North America, Latin America, Asia, and Australia also document circulation, with underdiagnosis common outside Europe. Overall, the study highlights Q fever as a persistent global zoonosis with underestimated burden, requiring strengthened surveillance, molecular epidemiology, and One Health approaches to mitigate human and animal health impacts.