title: Exposure to low doses of Coxiella burnetii caused high illness attack rates: Insights from combining human challenge and outbreak data.
abstract: BACKGROUND
  As a major zoonotic pathogen, characterization of the infectivity and pathogenicity of Coxiella burnetii is essential to understand Q-fever epidemiology.
  
  
  OBJECTIVE
  We want to extend a recently published human dose response model based on experimental challenge of young adult males to include other age groups and both genders. Additionally, we can estimate the spatial distribution of exposure based on observed outbreak data.
  
  
  METHODS
  Dose response assessment based on human challenge, is extended by including outbreak data, using location of cases as a proxy for exposure. This allows estimation of the influence of age and gender on the probability of developing symptoms of acute respiratory illness.
  
  
  RESULTS
  In an outbreak in Switzerland, in 1983, exposure to C. burnetii was shown to depend strongly on distance from the source. The susceptibility of males to develop Q-fever decreases with age, while in females, middle-aged women appear to have the lowest risk.
  
  
  CONCLUSIONS
  The published dose response model for Q-fever, based on experimental challenge of a small group of human volunteers, has been updated with data from a well studied outbreak. Infectivity estimates remain high, and even low doses (of 10 or fewer organisms) cause a high risk of illness.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands. Electronic address: j.brooke@umcutrecht.nl.
authors.forename: Russell John
authors.initials: RJ
authors.lastname: Brooke
authors.affiliation: Department of Infectious Diseases, Medical Microbiology and Hygiene, Heidelberg University Hospital, Heidelberg, Germany.
authors.forename: Nico T
authors.initials: NT
authors.lastname: Mutters
authors.affiliation: Unit of Infectious Diseases, Institut Central des Hopitaux Valaisans, Sion, Switzerland.
authors.forename: Olivier
authors.initials: O
authors.lastname: Péter
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands; Centre for Infectious Disease Control, RIVM, Bilthoven, The Netherlands.
authors.forename: Mirjam E E
authors.initials: ME
authors.lastname: Kretzschmar
authors.affiliation: Centre for Infectious Disease Control, RIVM, Bilthoven, The Netherlands; Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, GA, USA.
authors.forename: Peter F M
authors.initials: PF
authors.lastname: Teunis
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D016997:Coxiella burnetii / Q000472:pathogenicity*; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D008875:Middle Aged; D011778:Q Fever / Q000453:epidemiology*; D012737:Sex Factors; D013557:Switzerland / Q000453:epidemiology; D055815:Young Adult
keywords: Coxiella burnetii; Dose response; Exposure estimates; Outbreak; Q-fever