The mathematical transmission model was informed by all available epidemiological, biological, behavioural, and clinical data as relevant for the Australian population of IDUs, as well as trends in the number of syringes distributed through NSPs (Figure 1). The model was calibrated to accurately reflect the HIV and HCV epidemics in this population (Figure 2; cyan curves are 100 model simulations, the black solid curve represents the median, and dashed curves represent the interquartile range). The model describes the trends in notifications data, suggesting that the annual national incidence of HIV among IDUs has decreased from approximately 39 in 2000 to 24 in 2009; similarly annual national incidence of HCV has decreased from ~13,000 in 2000 to ~8,000 in 2009. The reduction in notifications is largely due to a decrease in the number of IDUs (results not shown; had the number of injectors remained steady, expected notifications would have also remained relatively stable). In Figure 2, HIV and HCV notifications data are shown along with the best 100 model simulations under conditions of actual NSP distribution of sterile injecting equipment units.

Figure 1: Annual number of needles and syringes distributed in Australia (1999-2008)

Text equivalent below for Figure 1: Annual number of needles and syringes distributed in Australia (1999-2008)Top of page

Text version of Figure 1

Figures in this description are approximate as they have been read from the graph.

Number of syringes distributed in Australia per year:
  • 1999 - 31,000,000
  • 2000 - 32,000,000
  • 2001 - 31,000,000
  • 2002 - 31,000,000
  • 2003 - 31,000,000
  • 2004 - 33,000,000
  • 2005 - 34,000,000
  • 2006 - 34,000,000
  • 2007 - 37,000,000
  • 2008 - 34,000,000

Figure 2: HIV and HCV notifications data among Australian IDUs and 100 model simulations for current NSP coverage (1999-2009)

Text equivalent below for Figure 2: HIV notifications data among Australian IDUs and 100 model simulations for current NSP coverage (1999-2009)Text equivalent below for Figure 2: HCV notifications data among Australian IDUs and 100 model simulations for current NSP coverage (1999-2009)

Text version of Figure 2

Figures in this description are approximate as they have been read from the graph.
Top of page
Figure 2 consists of two graphs:
  • Annual HIV incidence among Australian IDUs

    • The 100 model simulations decend gradually from a range of 30-45 in 1999 to 16-29 in 2009

    • The median of the model simulations decends gradually from 35 in 1999 to 22 in 2009

    • The lower quartile of the model simulations descends gradually from 32 in 1999 to 20 in 2009

    • The upper quartile of the model simulations descends gradually from 40 in 1999 to 24 in 2009

    • The notification data for annual incidence of HIV is:
      • 1999 - 33
      • 2000 - 30
      • 2001 - 40
      • 2002 - 20
      • 2003 - 30
      • 2004 - 38
      • 2005 - 30
      • 2006 - 28
      • 2007 - 14

  • Annual HCV incidence among Australian IDUs

    • The 100 model simulations decends sharply from a range of 13,500-16,600 in 1999 to 8,100-10,000 in 2003, before rising gradually to a range of 8,800-11,200 in 2009

    • The median of the model simulations decends gradually from 15,000 in 1999 to 8,800 in 2003, before rising gradually to 10,100 in 2009

    • The lower quartile of the model simulations descends sharply from 15,000 in 1999 to 8,500 in 2003, before rising gradually to 9,900 in 2009

    • The upper quartile of the model simulations descends sharply from 15,800 in 1999 to 9,000 in 2003, before rising gradually to 10,200 in 2009

    • The notification data for annual incidence of HCV is:
      • 1999 - 13,000
      • 2000 - 13,100
      • 2001 - 10,500
      • 2002 - 9,100
      • 2003 - 9,000
      • 2004 - 8,900
      • 2005 - 8,800