Table 1 Equation 1 parameters, values, and sources.

Transmission probability was calculated on the basis of Eq. 1. The parameters VL, s, ρ, and q used in Eq. 1 are described together with values and their ranges. Sources are identified, whether calculated in this study, taken from previously published data, or estimated from experts familiar with practices used by injecting drug users. IQR, interquartile range (Q1 to Q3).

ParameterDescription (units)Value (range)ScenarioSource
nNumber (#) of transferred HCV RNA
IUs by contaminated syringe
VL · ρ · sCalculated as described in
text and in Fig. 1
VLDonor’s viral load in blood
(RNA IU/ml)
Variable (0 to 6 log10 IU/ml)ExperimentalValues input for testing
(Fig. 4 and Table 1)
Time-dependent:
three primary acute-phase
viral kinetic patterns
Self-limiting, transient, and chronic
outcome (Fig. 5, A to C)
InC3 Study (1720)
Time-dependent:
three reinfection viral
kinetic patterns
Self-limiting (low and high titer) and
chronic outcome (Fig. 5, D to F)
sDonor blood as a fraction of the
mixture with illicit drugs (%)
25% (5–50%)Expert view
ρHCV RNA carry-over0.6% (0.02 to 2.6%)LDSSEstimated in the current
study (Fig. 2)
3.1% (1.4 to 7.2%)HDSS
0.12% (0.003 to 0.8%)LDSS + rinse
0.38% (0.03 to 0.77%)HDSS + rinse
qRatio of infectious doses to
HCV RNA IU
17% (IQR, 7–33%)Table S2 based on published
studies (8, 9, 11, 21, 30)