title: Tuberculosis in a South African prison - a transmission modelling analysis.
abstract: BACKGROUND
  Prisons are recognised internationally as institutions with very high tuberculosis (TB) burdens where transmission is predominantly determined by contact between infectious and susceptible prisoners. A recent South African court case described the conditions under which prisoners awaiting trial were kept. With the use of these data, a mathematical model was developed to explore the interactions between incarceration conditions and TB control measures.
  
  
  METHODS
  Cell dimensions, cell occupancy, lock-up time, TB incidence and treatment delays were derived from court evidence and judicial reports. Using the Wells-Riley equation and probability analyses of contact between prisoners, we estimated the current TB transmission probability within prison cells, and estimated transmission probabilities of improved levels of case finding in combination with implementation of national and international minimum standards for incarceration.
  
  
  RESULTS
  Levels of overcrowding (230%) in communal cells and poor TB case finding result in annual TB transmission risks of 90% per annum. Implementing current national or international cell occupancy recommendations would reduce TB transmission probabilities by 30% and 50%, respectively. Improved passive case finding, modest ventilation increase or decreased lock-up time would minimally impact on transmission if introduced individually. However, active case finding together with implementation of minimum national and international standards of incarceration could reduce transmission by 50% and 94%, respectively.
  
  
  CONCLUSIONS
  Current conditions of detention for awaiting-trial prisoners are highly conducive for spread of drug-sensitive and drug-resistant TB. Combinations of simple well-established scientific control measures should be implemented urgently.
authors.affiliation: Desmond Tutu HIV Centre, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, South Africa.
authors.forename: Simon
authors.initials: S
authors.lastname: Johnstone-Robertson
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Lawn
authors.forename: Alex
authors.initials: A
authors.lastname: Welte
authors.forename: Linda-Gail
authors.initials: LG
authors.lastname: Bekker
authors.forename: Robin
authors.initials: R
authors.lastname: Wood
mesh_terms: D003441:Crowding; D006801:Humans; D015233:Models, Statistical; D011330:Prisons / Q000592:standards / Q000706:statistics & numerical data; D013019:South Africa; D014376:Tuberculosis / Q000517:prevention & control / Q000635:transmission*