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Coxiella burnetii Infection Is Lower in Children than in Adults After Community Exposure: Overlooked Cause of Infrequent Q Fever Reporting in the Young

Hackert, Volker H. MD, MSc*†; Dukers-Muijrers, Nicole H.T.M. PhD*†; van Loo, Inge H.M. MD, PhD; Wegdam-Blans, Marjolijn MD, PhD; Somers, Carlijn MSc*; Hoebe, Christian J.P.A. MD, PhD*†

The Pediatric Infectious Disease Journal: December 2015 - Volume 34 - Issue 12 - p 1283–1288
doi: 10.1097/INF.0000000000000871
Original Studies

Background: Q fever is rarely reported in children/adolescents. Although lower reporting rates are commonly attributed to milder disease and subsequent underdiagnosis in infected children/adolescents, pertinent evidence is scarce. We present data from a large, well-defined single-point source outbreak of Q fever to fill this gap.

Methods: We compared (A) Q fever testing and notification rates in children/adolescents who were 0–19 years of age with those in adults 20+ years of age in October 2009; (B) serological attack rates of acute Q fever in children/adolescents with the rates in adults after on-source exposure on the outbreak farm’s premises; (C) incidence of Q fever infection in children/adolescents with that in adults after off-source exposure in the municipality located closest to the farm.

Results: (A) Children/adolescents represented 19.3% (59,404 of 307,348) of the study area population, 12.1% (149 of 1217) of all subjects tested in October 2009 and 4.3% (11 of 253) of notified laboratory-confirmed community cases. (B) Serological attack rate of acute Q fever in children with on-source exposure was 71% (12 of 17), similar to adults [68% (40 of 59)]. (C) Incidence of infection in children/adolescents after community (off-source) exposure was 4.5% (13 of 287) versus 11.0% (12 of 109) in adults (adjusted odds ratio: 0.36; 95% confidence interval: 0.16–0.84; P = 0.02). No children/adolescents reported clinical symptoms. Proportion of notified infections was significantly lower in children/adolescents (2.5%) than in adults (10.4%; risk ratio: 0.26; 95% confidence interval: 0.08–0.80, P = 0.02).

Conclusion: Notified Q fever was less frequent in children/adolescents than in adults. Although underrecognition contributed to this phenomenon, lower rates of infection in children after community exposure played an unexpected major role. On-source (presumed high-dose) exposure, by contrast, was associated with high serological and clinical attack rates not only in adults but also in children/adolescents. Our findings allow for improved age-specific clinical and public health risk assessment in Q fever outbreaks.

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From the *Department of Sexual Health, Infectious Diseases, and Environmental Health, South Limburg Public Health Service, Geleen, The Netherlands; Department of Medical Microbiology, School of Public Health and Primary Care, Maastricht University Medical Center, Maastricht, The Netherlands; and Department of Medical Microbiology, Laboratory for Pathology and Medical Microbiology (PAMM), Veldhoven, The Netherlands.

Accepted for publication March 31, 2015.

The Netherlands Organisation for Health Research and Development [50-50405-98-133] and the Dutch National Institute for Public Health and the Environment [001/2012 CIb/LCI/HvdK/ss] provided funding for this study. The authors have no conflicts of interest to disclose.

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Address for correspondence: Volker H. Hackert, MD, MSc, Department of Sexual Health, Infectious Diseases, and Environmental Health, South Limburg Public Health Service, PO Box 2022, 6160 HA Geleen, The Netherlands. E-mail:

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