title: Interim modelling analysis to validate reported increases in condom use and assess HIV infections averted among female sex workers and clients in southern India following a targeted HIV prevention programme.
abstract: OBJECTIVE
  This study assesses whether the observed declines in HIV prevalence since the beginning of the 'Avahan' India HIV/AIDS prevention initiative are consistent with self-reported increases in condom use by female sex workers (FSWs) in two districts of southern India, and provides estimates of the fraction of new infections averted among FSWs and clients due to increases in condom use in commercial sex after 2004.
  
  
  METHODS
  A deterministic compartmental model of HIV/sexually transmitted infection (STI) transmission incorporating heterogeneous sexual behaviour was developed, parameterised and fitted using data from two districts in Karnataka, India. Three hypotheses of condom use among FSWs were tested: (H(0)), that condom use increased in line with reported FSW survey data prior to the Avahan initiative but remained constant afterwards; (H(1)) that condom use increased following the Avahan initiative, in accordance with survey data; (H(2)) that condom use increased according to estimates derived from condom distribution data. The proportion of fits to HIV/STI prevalence data was examined to determine which hypothesis was most consistent.
  
  
  RESULTS
  For Mysore 0/36/82.7 fits were identified per million parameter sets explored under hypothesis H(0)/H(1)/H(2), respectively, while for Belgaum 9.7/8.3/0 fits were identified. The HIV epidemics in Belgaum and Mysore are both declining. In Mysore, increases in condom use during commercial sex between 2004 and 2009 may have averted 31.2% to 47.4% of new HIV infections in FSWs, while in Belgaum it may have averted 24.8% to 43.2%, if there was an increase in condom use.
  
  
  CONCLUSIONS
  Increased condom use following the Avahan intervention is likely to have played a role in curbing the HIV epidemic in Mysore. In Belgaum, given the limitations in available data, this method cannot be used alone to decide if there has been an increase in condom use.
authors.affiliation: Department of Infectious Disease Epidemiology, Imperial College, St Mary's Campus, London, UK. m.pickles@imperial.ac.uk
authors.forename: Michael
authors.initials: M
authors.lastname: Pickles
authors.forename: Anna M
authors.initials: AM
authors.lastname: Foss
authors.forename: Peter
authors.initials: P
authors.lastname: Vickerman
authors.forename: Kathleen
authors.initials: K
authors.lastname: Deering
authors.forename: Supriya
authors.initials: S
authors.lastname: Verma
authors.forename: Eric
authors.initials: E
authors.lastname: Demers
authors.forename: Reynold
authors.initials: R
authors.lastname: Washington
authors.forename: B M
authors.initials: BM
authors.lastname: Ramesh
authors.forename: Stephen
authors.initials: S
authors.lastname: Moses
authors.forename: Jamie
authors.initials: J
authors.lastname: Blanchard
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Lowndes
authors.forename: Michel
authors.initials: M
authors.lastname: Alary
authors.forename: Sushena
authors.initials: S
authors.lastname: Reza-Paul
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Boily
mesh_terms: D000328:Adult; D017280:Condoms / Q000706:statistics & numerical data*; D004196:Disease Outbreaks; D004812:Epidemiologic Methods; D005260:Female; D015658:HIV Infections / Q000453:epidemiology / Q000517:prevention & control* / Q000635:transmission; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D007194:India / Q000453:epidemiology; D008297:Male; D015397:Program Evaluation; D021841:Safe Sex / Q000706:statistics & numerical data*; D011477:Sex Work / Q000706:statistics & numerical data*