Natural history parameters for HIV infection receiving first-line treatment (Source: ATHENA cohort data17) Refer to the technical appendix for details
| Parameter | Value | Unit | |
| Log10 viral load at treatment initiation (normal distribution) | Mean | 5.1 | Log copies per microlitre |
| Variance | 0.40 | ||
| Fraction achieving suppression* | 0.70 | Fraction | |
| Fraction with good adherence† | 0.94 | Fraction | |
| Waiting time until viral suppression, if suppression and good adherence (exponential distribution) | Median | 5.38 | Months |
| Waiting time until viral suppression, if suppression and not good adherence (exponential distribution) | Median | 5.92 | Months |
| Waiting time (months) until viral rebound, if good adherence (double Weibull distribution), assuming shortened (s) survival times (used unless otherwise stated) or extended (e) survival. | Shape1 | 1.14 (e) 10.23 (s) | Months |
| Scale1 | 456.65 (e) 153.25 (s) | ||
| Shape2 | 1.92 (e) 1.25 (s) | ||
| Scale2 | 20.70 (e) 41.58 (s) | ||
| Weighting | 0.91 (e) 0.77 (s) | ||
| Waiting time until viral rebound, if not good adherence (Weibull distribution) | Shape1 | 1.14 | Months |
| Scale1 | 132.86 | ||
| Rate of increase in log10 viral load on rebound, if good adherence‡ | Rate | 0.07 (se=0.002) | Log10 copies per microlitre per month |
| Rate of increase in log10 viral load on rebound, if not good adherence‡ | Rate | 0.16 (se=0.01) | Log10 copies per microlitre per month |
| Maximum survival time with non-suppressed viral load | Max | 1 | Years |
| Log10 viral load if no suppression (normal distribution) | Mean | 3.80 | Log copies per microlitre |
| Variance | 0.84 |
↵* Suppression is defined as at least two consecutive viral load measurements <500 HIV RNA copies per millilitre.
↵† Adherence is classified as good or poor based on the measurement of plasma drug levels.
↵‡ At all times in the simulation, viral load is limited to less than or equal to the 95th centile of viral loads at treatment initiation in the ATHENA data (equal to six log-copies).