Q fever outbreak in an urban area following a school-farm visit

BACKGROUND AND OBJECTIVE: The aim of this study was to describe an outbreak of Q fever in a group of people (day care centre for mental-handicapped individuals) previously exposed to animals in a school-farm. PATIENTS AND METHOD: A retrospective cohort study among the 25 mental-handicapped individuals and the 30 workers of the centre was performed. The information about symptoms and signs and antecedents of exposition was obtained by an epidemiological survey and a clinical-epidemiological case definition was established. Serum samples from 29 people (5 mental-handicapped individuals and 24 workers) were processed for serology (indirect immunofluorescence against Coxielia burnetii). RESULTS: Twenty two cases of Q fever were detected. Ten were confirmed by serology (6 of them asymptomatic). More frequent symptoms were fever (100%), anorexia (81.3%), asthenia (68.8%) and non-productive cough (56.3%) among the 16 clinical cases. The risk of acute infection was 8.6 times higher in individuals of the centre that visited the school-farm (95% CI, 1.26-58.27). CONCLUSIONS; The investigation of the epidemiological antecedents allowed to detect and confirm a Q fever outbreak, to identify the probable source of exposition and to orientate the clinical and serological diagnosis.