# Forecasting epidemic trajectories if injecting behaviour changes

Page last updated: 2009

The mathematical model was used to calculate projections of the expected number of HIV and HCV cases in the future if the average frequency of injecting changes (by the stated amount in the figure captions over a ten year period). Not surprising, we found that changes in average frequency of injecting can have noticeable effects on HIV and HCV incidence among IDUs (Figure 17, Figure 18, Figure 19 and Figure 20).

## Figure 17: Projected HIV and HCV cases among Australian IDUs if the average frequency of injecting decreases by 25% (2010-2019) ### Text version of Figure 17

Top of pageFigure 17 consists of two graphs:
• Projected annual HIV incidence among Australian IDUs if the average frequency of injecting decreases by 25% (2010-2019)

• The 100 model simulations decrease gradually from a range of 10-42 in 2009 to a range of 5-22 in 2011 and decrease gradually to 3-13 in 2020.

• The median of the model simulations decreases gradually from 24 in 2009 to 12 in 2011 and decreases gradually to 8 in 2020.

• The lower quartile of the model simulations decreases gradually from 18 in 2009 to 10 in 2011 and decreases gradually to 5 in 2020.

• The upper quartile of the model simulations decreases gradually from 30 in 2009 to 17 in 2011 and decreases gradually to 9 in 2020.

• Projected annual HCV incidence among Australian IDUs if the average frequency of injecting decreases by 25% (2010-2019)

• The 100 model simulations decrease sharply from a range of 7,800-16,200 in 2009 to a range of 4,800-10,500 in 2011 and increase gradually to 6,000-14,000 in 2020.

• The median of the model simulations decreases sharply from 11,800 in 2009 to 7,800 in 2011, before increasing gradually to 9,500 in 2020.

• The lower quartile of the model simulations decreases sharply from 10,500 in 2009 to 6,800 in 2011, before increasing gradually to 8,200 in 2020.

• The upper quartile of the model simulations decreases sharply from 13,000 in 2009 to 8,000 in 2011, before increasing gradually to 10,500 in 2020.

## Figure 18: Projected HIV and HCV cases among Australian IDUs if the average frequency of injecting decreases by 10% (2010-2019) ### Text version of Figure 18

Top of pageFigure 18 consists of two graphs:
• Projected annual HIV incidence among Australian IDUs if the average frequency of injecting decreases by 10% (2010-2019)

• The 100 model simulations decrease slightly from a range of 10-42 in 2009 to a range of 8-33 in 2011, before decreasing gradually to 5-21 in 2020.

• The median of the model simulations decreases slightly from 24 in 2009 to 19 in 2011, before decreasing gradually to 22 in 2020.

• The lower quartile of the model simulations decreases slightly from 19 in 2009 to 12 in 2011, before decreasing gradually to 10 in 2020.

• The upper quartile of the model simulations decreases slightly from 31 in 2009 to 13 in 2011, before decreasing gradually to 17 in 2020.

• Projected annual HCV incidence among Australian IDUs if the average frequency of injecting decreases by 10% (2010-2019)

• The 100 model simulations decreases slightly from a range of 7,800-16,000 in 2009 to a range of 6,500-14,500 in 2011 and increase gradually to 7,800-16,000 in 2020.

• The median of the model simulations decreases slightly from 11,800 in 2009 to 10,000 in 2011 and increases gradually to 11,800 in 2020.

• The lower quartile of the model simulations decreases slightly from 10,800 in 2009 to 9,000 in 2011 and increases gradually to 10,800 in 2020.

• The upper quartile of the model simulations decreases slightly from 13,000 in 2009 to 11,200 in 2011 and increases gradually to13,000 in 2020.

## Figure 19: Projected HIV and HCV cases among Australian IDUs if the average frequency of injecting increases by 10% (2010-2019) ### Text version of Figure 19

Top of pageFigure 19 consists of two graphs:
• Projected annual HIV incidence among Australian IDUs if the average frequency of injecting increases by 10% (2010-2019)

• The 100 model simulations increase slightly from a range of 10-42 in 2009 to a range of 13-50 in 2011, before decreasing gradually to 10-47 in 2020.

• The median of the model simulations increases slightly from 24 in 2009 to 29 in 2011, before decreasing gradually to 25 in 2020.

• The lower quartile of the model simulations increases slightly from 18 in 2009 to 21 in 2011, before decreasing gradually to 19 in 2020.

• The upper quartile of the model simulations increases slightly from 31 in 2009 to 36 in 2011, before decreasing gradually to 32 in 2020.

• Projected annual HCV incidence among Australian IDUs if the average frequency of injecting increases by 10% (2010-2019)

• The 100 model simulations increases slightly from a range of 7,800-16,500 in 2009 to a range of 9,000-18,500 in 2011 and the upper limit decreases slightly to 9,000-18,000 in 2020.

• The median of the model simulations increases slightly from 11,900 in 2009 to 15,000 in 2011 and remains steady to 2020.

• The lower quartile of the model simulations increases slightly from 10,800 in 2009 to 13,000 in 2011 and remains steady to 2020.

• The upper quartile of the model simulations increases slightly from 13,000 in 2009 to 15,500 in 2011 and decreases slightly to 15,300 in 2020.

## Figure 20: Projected HIV and HCV cases among Australian IDUs if the average frequency of injecting increases by 25% (2010-2019) ### Text version of Figure 20

Top of pageFigure 20 consists of two graphs:
• Projected annual HIV incidence among Australian IDUs if the average frequency of injecting increases by 25% (2010-2019)

• The 100 model simulations increase sharply from a range of 10-43 in 2009 to a range of 17-68 in 2011, before increasing gradually to 18-82 in 2020.

• The median of the model simulations increases sharply from 24 in 2009 to 38 in 2011, before increasing gradually to 45 in 2020.

• The lower quartile of the model simulations increases sharply from 18 in 2009 to 28 in 2011, before increasing gradually to 32 in 2020.

• The upper quartile of the model simulations increases sharply from 32 in 2009 to 49 in 2011, before increasing gradually to 57 in 2020.

• Projected annual HCV incidence among Australian IDUs if the average frequency of injecting increases by 25% (2011-2019)

• The 100 model simulations increase sharply from a range of 7,800-16,500 in 2009 to a range of 11,800-23,500 in 2011 and decrease gradually to 10,500-19,500 in 2020.

• The median of the model simulations increases sharply from 11,800 in 2009 to 17,000 in 2011, before decreasing gradually to 15,000 in 2020.

• The lower quartile of the model simulations increases sharply from 10,500 in 2009 to 16,000 in 2011, before decreasing gradually to 13,200 in 2020.

• The upper quartile of the model simulations increases sharply from 13,000 in 2009 to 19,500 in 2011, before decreasing gradually to 16,000 in 2020.
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