title: Force of tuberculosis infection among adolescents in a high HIV and TB prevalence community: a cross-sectional observation study.
abstract: BACKGROUND
  Understanding of the transmission dynamics of tuberculosis (TB) in high TB and HIV prevalent settings is required in order to develop effective intervention strategies for TB control. However, there are little data assessing incidence of TB infection in adolescents in these settings.
  
  
  METHODS
  We performed a tuberculin skin test (TST) and HIV survey among secondary school learners in a high HIV and TB prevalence community. TST responses to purified protein derivative RT23 were read after 3 days. HIV-infection was assessed using Orasure® collection device and ELISA testing. The results of the HIV-uninfected participants were combined with those from previous surveys among primary school learners in the same community, and force of TB infection was calculated by age.
  
  
  RESULTS
  The age of 820 secondary school participants ranged from 13 to 22 years. 159 participants had participated in the primary school surveys. At a 10 mm cut-off, prevalence of TB infection among HIV-uninfected and first time participants, was 54% (n = 334/620). HIV prevalence was 5% (n = 40/816). HIV infection was not significantly associated with TST positivity (p = 0.07). In the combined survey dataset, TB prevalence was 45% (n = 645/1451), and was associated with increasing age and male gender. Force of infection increased with age, from 3% to 7.3% in adolescents ≥ 20 years of age.
  
  
  CONCLUSIONS
  We show a high force of infection among adolescents, positively associated with increasing age. We postulate this is due to increased social contact with infectious TB cases. Control of the TB epidemic in this setting will require reducing the force of infection.
authors.affiliation: Desmond Tutu HIV Centre, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa. keren.middelkoop@hiv-research.org.za
authors.forename: Keren
authors.initials: K
authors.lastname: Middelkoop
authors.forename: Linda-Gail
authors.initials: LG
authors.lastname: Bekker
authors.forename: Hua
authors.initials: H
authors.lastname: Liang
authors.forename: Lisa D H
authors.initials: LD
authors.lastname: Aquino
authors.forename: Elaine
authors.initials: E
authors.lastname: Sebastian
authors.forename: Landon
authors.initials: L
authors.lastname: Myer
authors.forename: Robin
authors.initials: R
authors.lastname: Wood
mesh_terms: D000293:Adolescent; D000367:Age Factors; D003430:Cross-Sectional Studies; D005260:Female; D015658:HIV Infections / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology*; D006801:Humans; D008297:Male; D015995:Prevalence; D012111:Residence Characteristics; D013019:South Africa / Q000453:epidemiology; D014374:Tuberculin Test; D014376:Tuberculosis / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology*; D055815:Young Adult