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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
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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.

Supplemental Digital Content is available in the text.

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.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website (www.pidj.com).

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: volker.hackert@ggdzl.nl.

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