title: Coxiella burnetii Infection Is Lower in Children than in Adults After Community Exposure: Overlooked Cause of Infrequent Q Fever Reporting in the Young.
abstract: 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: 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.
authors.forename: Volker H
authors.initials: VH
authors.lastname: Hackert
authors.forename: Nicole H T M
authors.initials: NH
authors.lastname: Dukers-Muijrers
authors.forename: Inge H M
authors.initials: IH
authors.lastname: van Loo
authors.forename: Marjolijn
authors.initials: M
authors.lastname: Wegdam-Blans
authors.forename: Carlijn
authors.initials: C
authors.lastname: Somers
authors.forename: Christian J P A
authors.initials: CJ
authors.lastname: Hoebe
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D016997:Coxiella burnetii; D003430:Cross-Sectional Studies; D018563:Disease Notification / Q000706:statistics & numerical data*; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D009426:Netherlands; D011778:Q Fever / Q000453:epidemiology*; D055815:Young Adult