Table 3 HIV and HCV biological model parameters with uncertainty ranges for fitting algorithm

Biological model parameter	Value used	Data source
HIV biological model parameters
HIV transmission probability per syringe sharing event	0.14–1.41%	Reference 3
Cofactor increase in HIV transmission probability during
Initial period of high viraemia	7.5–15	References 44–46
Pre-AIDS period of high viraemia	3–6	Reference 46
Duration of initial period of high viraemia	1.5–2.5 months	References 46, 47
Duration of pre-AIDS period of high viraemia	12–24 months	Reference 46
Median duration until severe morbidity or death	75–92 months	Indian estimates used48 49
Effectiveness of cleaning syringes for disinfecting against HIV (mainly water used)	52% (37% to 67%)*	Reference 50
HCV biological model parameters
HCV transmission probability if HIV negative	1.5–14%	See supplementary material3 4
HCV transmission probability if HIV positive relative to if HIV negative	RR 1.0–3.7	See supplementary material4 33 51
Duration of HCV acute phase of infection	3–24 months	References 22, 52, 53
Proportion of HCV-infected subjects that resolve infection:
Among HIV negatives	26% (20% to 50%)	Reference 6
Among HIV positives relative to HIV negatives	RR 0.21–0.58	References 28, 29, 36, 54
Proportion of resolved infected subjects that become immune:		References 23–25, 27, 35
If HIV negative	0–100%
If HIV positive relative to HIV negatives	RR 0.3–0.5	Few data25 35
Effectiveness of cleaning syringes for disinfecting against HCV (mainly water used)	Assumed same effectiveness as HIV	Few data55