The mathematical model was used to project the expected number of HIV and HCV cases in the future according to scenarios whereby current syringe distribution levels are maintained or if there are increases or decreases in the provision of syringes through NSPs. The model simulated the epidemics up to the year 2079 for economic analyses but epidemic forecasts are shown to the year 2019. Different coverage rates were simulated across the diverse groups of IDUs (Figures 5-12). Simulations for average changes in syringe use across all groups, proportional to syringe distribution are shown in this report.

It is forecasted that under current conditions, HIV incidence among Australian IDUs will continue to decline slowly and there will be slight increases in HCV incidence (Figure 5). If NSPs cease, then relatively large increases in both HIV and HCV could be expected (Figure 6); HCV incidence will return to a higher level within a few years but HIV incidence will continue to expand over the medium-to-long term. Reductions in the distribution of sterile injecting equipment can be expected to lead to detrimental epidemiological consequences (Figure 7, Figure 8 and Figure 9). However, epidemics are not highly sensitive to perturbations in NSP service; small changes are expected to have only modest epidemiological consequences.

Significant public health benefits can be attained with further expansion of sterile injecting equipment distribution (Figure 10, Figure 11 and Figure 12). Because HIV incidence is already low, NSP expansion is unlikely to have a noticeable effect on HIV transmission among IDUs. However, noticeable reductions in HCV incidence can be attained with NSP expansion. It is not feasible to see large reductions in HCV, towards eradication, with NSPs. But it could be expected that declines will occur in the short term before incidence rebounds to an endemic level lower than current levels.

Figure 5: Projected HIV and HCV cases among Australian IDUs with current conditions of syringe distribution and coverage maintained (2010-2019)

Text equivalent below for Figure 5: Projected HIV cases among Australian IDUs with current conditions of syringe distribution and coverage maintained (2010-2019)Text equivalent below for Figure 5: Projected HCV cases among Australian IDUs with current conditions of syringe distribution and coverage maintained (2010-2019)

Text version of Figure 5

Figures in this description are approximate as they have been read from the graph.
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Figure 5 consists of two graphs:
  • Projected anuual HIV incidence among Australian IDUs with current conditions of syringe distribution and coverage maintained (2010-2019)

    • The 100 model simulations decrease gradually from a range of 10-43 in 2009 to 8-30 in 2020.

    • The median of the model simulations decreases gradually from 25 in 1999 to 18 in 2020.

    • The lower quartile of the model simulations decreases gradually from 18 in 1999 to 12 in 2020.

    • The upper quartile of the model simulations decreases gradually from 31 in 1999 to 23 in 2020.

  • Projected annual HCV incidence among Australian IDUs with current conditions of syringe distribution and coverage maintained (2010-2019)

    • The 100 model simulations rise gradually from a range of 7,900-16,100 in 2009 to a range of 8,500-17,000 in 2014 and remain level until 2020.

    • The median of the model simulations rises gradually from 12,000 in 2009 to 13,000 in 2020.

    • The lower quartile of the model simulations rises gradually from 10,900 in 2009 to 12,000 in 2020.

    • The upper quartile of the model simulations rises gradually from 13,000 in 2009 to 14,000 in 2020.

Figure 6: Projected HIV and HCV cases among Australian IDUs if NSPs cease to distribute injecting equipment (2010-2019)

Text equivalent below for Figure 6: Projected HIV cases among Australian IDUs if NSPs cease to distribute injecting equipment (2010-2019)Text equivalent below for Figure 6: Projected HCV cases among Australian IDUs if NSPs cease to distribute injecting equipment (2010-2019)

Text version of Figure 6

Figures in this description are approximate as they have been read from the graph.
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Figure 6 consists of two graphs:
  • Projected annual HIV incidence among Australian IDUs if NSPs cease to distribute injecting equipment (2010-2019)

    • The 100 model simulations increase gradually from 0 in 2010 to a range of 1,000-9,500 in 2016, before increasing dramatically to 3,000-15,000 in 2020.

    • The median of the model simulations increases from 0 in 2010 to 4,000 in 2016, before increasing dramatically to 16,000 in 2020.

    • The lower quartile of the model simulations increases from 0 in 2010 to 3,000 in 2016, before increasing dramatically to 9,000 in 2020.

    • The upper quartile of the model simulations increases from 0 in 2010 to 5,000 in 2016, before increasing dramatically to 21,000 in 2020.

  • Projected annual HCV incidence among Australian IDUs if NSPs cease to distribute injecting equipment (2010-2019)

    • The 100 model simulations spike from a range of 9,000-19,000 in 2009 to a range of 30,000-46,000 in 2010, decrease dramatically to 21,000-32,000 in 2011, and level off at 14,000-23,000 in 2014, ending at 14,000-24,000 in 2020.

    • The median of the model simulations spikes from 13,000 in 2009 to 37,000 in 2010, before decreasing dramatically to 19,000 in 2014 and remaining level to 2020.

    • The lower quartile of the model simulations spikes from 12,000 in 2009 to 35,000 in 2010, decreasing dramatically to 17,000 in 2014 and remaining level to 2020.

    • The upper quartile of the model simulations spikes from 14,000 in 2009 to 41,000 in 2010, decreasing dramatically to 20,000 in 2014 and remaining level to 2020.

Figure 7: Projected HIV and HCV cases among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 50% (2010-2019)

Text equivalent below for Figure 7: Projected HIV cases among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 50% (2010-2019)Text equivalent below for Figure 7: Projected HCV cases among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 50% (2010-2019)

Text version of Figure 7

Figures in this description are approximate as they have been read from the graph.
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Figure 7 consists of two graphs:
  • Projected annual HIV incidence among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 50%

    • The 100 model simulations increase dramatically from a range of 10-42 in 2009 to a range of 22-90 in 2011, before increasing gradually to 30-140+ by 2020.

    • The median of the model simulations increases dramatically from 25 in 2009 to 50 in 2011, before increasing gradually to 85 in 2020.

    • The lower quartile of the model simulations increases dramatically from 18 in 2009 to 36 in 2011, before increasing gradually to 61 in 2020.

    • The upper quartile of the model simulations increases dramatically from 32 in 2009 to 62 in 2011, before increasing gradually to 108 in 2020.

  • Projected annual HCV incidence among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 50%

    • The 100 model simulations increase dramatically from a range of 8,000-16,500 in 2009 to a range of 14,000-27,000 in 2011 before decreasing gradually to 11,000-21,000 in 2020.

    • The median of the model simulations increases dramatically from 12,000 in 2009 to 20,800 in 2011, before decreasing gradually to 19,000 in 2020.

    • The lower quartile of the model simulations increases dramatically from 11,000 in 2009 to 19,000 in 2011, before decreasing gradually to 14,300 in 2020.

    • The upper quartile of the model simulations increases dramatically from 13,000 in 2009 to 22,500 in 2011, before decreasing gradually to 17,000 in 2020.

Figure 8: Projected HIV and HCV cases among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 25% (2010-2019)

Text equivalent below for Figure 8: Projected HIV cases among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 25% (2010-2019)Text equivalent below for Figure 8: Projected HCV cases among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 25% (2010-2019)

Text version of Figure 8

Figures in this description are approximate as they have been read from the graph.
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Figure 8 consists of two graphs:
  • Projected annual HIV incidence among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 25% (2010-2019)

    • The 100 model simulations increase dramatically from a range of 10-42 in 2009 to a range of 12-55 in 2011 and remain level to 2020.

    • The median of the model simulations increases dramatically from 25 in 2009 to 30 in 2011 and remains level to 2020.

    • The lower quartile of the model simulations increases dramatically from 18 in 2009 to 24 in 2011 and remains level to 2020.

    • The upper quartile of the model simulations increases dramatically from 32 in 2009 to 40 in 2011 and remains level to 2020.

  • Projected annual HCV incidence among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 25% (2010-2019)

    • The 100 model simulations increase dramatically from a range of 8,000-16,500 in 2009 to a range of 10,000-20.500 in 2011 and decrease gradually to 9,800-18,500 in 2020.

    • The median of the model simulations increases dramatically from 12,000 in 2009 to 15,000 in 2011, before decreasing gradually to 14,000 in 2020.

    • The lower quartile of the model simulations increases dramatically from 11,000 in 2009 to 13,500 in 2011, before decreasing gradually to 13,000 in 2020.

    • The upper quartile of the model simulations increases dramatically from 13,000 in 2009 to 17,000 in 2011, before decreasing gradually to 15,500 in 2020.

Figure 9: Projected HIV and HCV cases among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 10% (2010-2019)

Text equivalent below for Figure 9: Projected HIV cases among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 10% (2010-2019)Text equivalent below for Figure 9: Projected HCV cases among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 10% (2010-2019)

Text version of Figure 9

Figures in this description are approximate as they have been read from the graph.
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Figure 9 consists of two graphs:
  • Projected annual HIV incidence among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 10% (2010-2019)

    • The 100 model simulations increase slightly from a range of 10-44 in 2009 to a range of 11-45 in 2011, before decreasing gradually to 10-38 in 2020.

    • The median of the model simulations increases slightly from 24 in 2009 to 25 in 2011, before decreasing gradually to 23 in 2020.

    • The lower quartile of the model simulations increases slightly from 18 in 2009 to 20 in 2011, before decreasing gradually to 17 in 2020.

    • The upper quartile of the model simulations increases slightly from 31 in 2009 to 33 in 2011, before decreasing gradually to 26 in 2020.

  • Projected annual HCV incidence among Australian IDUs if NSPs decrease overall distribution of injecting equipment by 10% (2010-2019)

    • The 100 model simulations increase dramatically from a range of 7,800-16,500 in 2009 to a range of 8,800-18,000 in 2011 and remain level to 2020.

    • The median of the model simulations increases gradually from 11,900 in 2009 to 13,000 in 2011 and remains level to 2020.

    • The lower quartile of the model simulations increases gradually from 10,800 in 2009 to 12,000 in 2011 and remains level to 2020.

    • The upper quartile of the model simulations increases gradually from 13,000 in 2009 to 14,500 in 2011 and remains level to 2020.

Figure 10: Projected HIV and HCV cases among Australian IDUs if NSPs increase overall distribution of injecting equipment by 10% (2010-2019)

Text equivalent below for Figure 10: Projected HIV cases among Australian IDUs if NSPs increase overall distribution of injecting equipment by 10% (2010-2019)Text equivalent below for Figure 10: Projected HCV cases among Australian IDUs if NSPs increase overall distribution of injecting equipment by 10% (2010-2019)

Text version of Figure 10

Figures in this description are approximate as they have been read from the graph.
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Figure 10 consists of two graphs:
  • Projected annual HIV incidence among Australian IDUs if NSPs increase overall distribution of injecting equipment by 10% (2010-2019)

    • The 100 model simulations decrease gradually from a range of 10-42 in 2009 to a range of 6-30 in 2020.

    • The median of the model simulations decreases gradually from 24 in 2009 to 15 in 2020.

    • The lower quartile of the model simulations decreases gradually from 18 in 2009 to 11 in 2020.

    • The upper quartile of the model simulations decreases gradually from 31 in 2009 to 20 in 2020.

  • Projected annual HCV incidence among Australian IDUs if NSPs increase overall distribution of injecting equipment by 10% (2010-2019)

    • The 100 model simulations decrease gradually from a range of 7,800-16,500 in 2009 to a range of 7,000-15.500 in 2011 and increase gradually to 8,100-16,800 in 2020.

    • The median of the model simulations decreases gradually from 11,800 in 2009 to 11,000 in 2011, before increasing gradually to 12,500 in 2020.

    • The lower quartile of the model simulations decreases gradually from 10,500 in 2009 to 10,000 in 2011, before increasing gradually to 11,500 in 2020.

    • The upper quartile of the model simulations increases decreases gradually 13,000 in 2009 to 12,200 in 2011, before increasing gradually to 13,800 in 2020.

Figure 11: Projected HIV and HCV cases among Australian IDUs if NSPs increase overall distribution of injecting equipment by 25% (2010-2019)

Text equivalent below for Figure 11: Projected HIV cases among Australian IDUs if NSPs increase overall distribution of injecting equipment by 25% (2010-2019)Text equivalent below for Figure 11: Projected HCV cases among Australian IDUs if NSPs increase overall distribution of injecting equipment by 25% (2010-2019)

Text version of Figure 11

Figures in this description are approximate as they have been read from the graph.
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Figure 11 consists of two graphs:
  • Projected annual HIV incidence among Australian IDUs if NSPs increase overall distribution of injecting equipment by 25% (2010-2019)

    • The 100 model simulations decrease gradually from a range of 10-42 in 2009 to a range of 8-35 in 2011 and decrease steadily to 5-22 in 2020.

    • The median of the model simulations decreases gradually from 25 in 2009 to 18 in 2011 and decreases steadily to 11 in 2020.

    • The lower quartile of the model simulations decreases gradually from 18 in 2009 to 14 in 2011 and decreases steadily to 9 in 2020.

    • The upper quartile of the model simulations decreases gradually from 32 in 2009 to 25 in 2011 and decreases steadily to 16 in 2020.

  • Projected annual HCV incidence among Australian IDUs if NSPs increase overall distribution of injecting equipment by 25% (2010-2019)

    • The 100 model simulations decrease dramatically from a range of 7,800-16,200 in 2009 to a range of 6,500-13,800 in 2011 and increase gradually to 7,800-16,000 in 2020.

    • The median of the model simulations decreases dramatically from 12,000 in 2009 to 10,000 in 2011, before increasing gradually to 12,000 in 2020.

    • The lower quartile of the model simulations decreases dramatically from 10,800 in 2009 to 8,800 in 2011, before increasing gradually to 10,800 in 2020.

    • The upper quartile of the model simulations decreases dramatically from 13,000 in 2009 to 11,000 in 2011, before increasing gradually to 13,000 in 2020.

Figure 12: Projected HIV and HCV cases among Australian IDUs if NSPs increase overall distribution of injecting equipment by 50% (2010-2019)

Text equivalent below for Figure 12: Projected HIV cases among Australian IDUs if NSPs increase overall distribution of injecting equipment by 50% (2010-2019)Text equivalent below for Figure 12: Projected HCV cases among Australian IDUs if NSPs increase overall distribution of injecting equipment by 50% (2010-2019)

Text version of Figure 12

Figures in this description are approximate as they have been read from the graph.
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Figure 12 consists of two graphs:
  • Projected annual HIV incidence among Australian IDUs if NSPs increase overall distribution of injecting equipment by 50% (2010-2019)

    • The 100 model simulations decrease gradually from a range of 10-42 in 2009 to a range of 8-26 in 2011 and decrease steadily to 4-18 in 2020.

    • The median of the model simulations decreases gradually from 26 in 2009 to 15 in 2011 and decreases steadily to 9 in 2020.

    • The lower quartile of the model simulations decreases gradually from 18 in 2009 to 11 in 2011 and decreases steadily to 8 in 2020.

    • The upper quartile of the model simulations decreases gradually from 32 in 2009 to 20 in 2011 and decreases steadily to 11 in 2020.

  • Projected annual HCV incidence among Australian IDUs if NSPs increase overall distribution of injecting equipment by 50% (2010-2019)

    • The 100 model simulations decrease dramatically from a range of 7,800-16,200 in 2009 to a range of 5,500-12,000 in 2011 and increase gradually to 6,800-15,000 in 2020.

    • The median of the model simulations decreases dramatically from 11,800 in 2009 to 8,200 in 2011, before increasing gradually to 10,800 in 2020.

    • The lower quartile of the model simulations decreases dramatically from 10,800 in 2009 to 7,800 in 2011, before increasing gradually to 9,800 in 2020.

    • The upper quartile of the model simulations decreases dramatically from 13,000 in 2009 to 9,800 in 2011, before increasing gradually to 11,800 in 2020.