title: Spatio-temporal analysis of tuberculous infection risk among clients of a homeless shelter during an outbreak.
abstract: METHODS
  British Columbia (BC) has a low incidence of tuberculosis (TB), with the burden of endogenously acquired disease concentrated among vulnerable populations, including the homeless. In May 2008, a TB outbreak began in a BC homeless shelter, with a single index case seeding multiple secondary cases within the shelter.
  
  
  OBJECTIVE
  To use nightly shelter records to quantify the risk of latent tuberculous infection (LTBI) among shelter clients as a function of their sleeping distance from and duration of exposure to the index case.
  
  
  METHODS
  Distance and duration of exposure were visualised and assessed using logistic regression with LTBI status as outcome. We used a novel machine learning approach to establish exposure thresholds that optimally separated infected and non-infected individuals.
  
  
  RESULTS
  Of 161 exposed shelter clients, 58 had a recorded outcome of infected (n = 39) or non-infected (n = 19). Only duration of exposure to the index was associated with increased odds of infection (OR 1.26); stays of ⩾ 5 nights put shelter clients at higher odds of infection (OR 4.97).
  
  
  CONCLUSIONS
  The unique data set and analytical approach suggested that, in a shelter environment, long-term clients are at highest risk of LTBI and should be prioritised for screening during an outbreak investigation.
authors.affiliation: Communicable Disease Prevention and Control Services, British Columbia Centre for Disease Control, Vancouver, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Crisan
authors.affiliation: Department of Microbiology & Immunology, University of British Columbia, Vancouver, Canada.
authors.forename: H Y
authors.initials: HY
authors.lastname: Wong
authors.affiliation: Clinical Prevention Services, British Columbia Centre for Disease Control, Vancouver, Canada.
authors.forename: J C
authors.initials: JC
authors.lastname: Johnston
authors.affiliation: British Columbia Public Health Microbiology and Reference Laboratory, Vancouver, British Columbia, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Tang
authors.affiliation: Department of Mathematics, Imperial College London, London, UK.
authors.forename: C
authors.initials: C
authors.lastname: Colijn
authors.affiliation: Communicable Disease Prevention and Control Services, British Columbia Centre for Disease Control, Vancouver, Canada; School of Population and Public Health, University of British Columbia, Vancouver, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Otterstatter
authors.affiliation: Interior Health Authority, Kelowna, British Columbia, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Hiscoe
authors.affiliation: Interior Health Authority, Kelowna, British Columbia, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Parker
authors.affiliation: Interior Health Authority, Kelowna, British Columbia, Canada.
authors.forename: S L
authors.initials: SL
authors.lastname: Pollock
authors.affiliation: Communicable Disease Prevention and Control Services, British Columbia Centre for Disease Control, Vancouver, Canada; School of Population and Public Health, University of British Columbia, Vancouver, Canada.
authors.forename: J L
authors.initials: JL
authors.lastname: Gardy
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis*; D001955:British Columbia / Q000453:epidemiology; D004196:Disease Outbreaks; D004781:Environmental Exposure; D006703:Ill-Housed Persons / Q000706:statistics & numerical data*; D006798:Housing; D006801:Humans; D055985:Latent Tuberculosis / Q000453:epidemiology*; D016015:Logistic Models; D012307:Risk Factors; D062211:Spatio-Temporal Analysis