Parameters and values incorporated into the model.

iGeometrically averaged Deff for HIV was previously measured to be 0.25 µm2/s, but with substantial fraction of viruses exhibiting more rapid mobility. For the current analysis, we used 1.27 µm2/s, which represented the top 25th percentile of virus mobility; this is in reasonable agreement with a more recent study of HIV diffusion in genital secretions [53]. iiEstimated based on a median semen volume of 3.0 mL [48], and 2.8×105 HIV-1 RNA copies/mL, which represents the upper limit of HIV-1 RNA copies/mL in seminal plasma from [47]. This is in reasonable agreement with another report by Chakraboty el al., which estimated 5×105 HIV-1 RNA copies/ejaculate, with a maximum of about 2×107 HIV-1 RNA copies/ejaculate [54]. iiiThe mean surface area of the vagina in the native state was previously estimated to be ∼90 cm2 by injection of vinyl polysiloxane casts vaginally. Alternatively, surface area of vaginal lumen may also be inferred by the surface area of erect penis (average ∼200 cm2) assuming complete insertion into the vagina. We took the average from the two approaches. ivIn the Materials and Methods section, HCVM is referred to as d and HCVM+HSemen = L. vHCVM estimated by VCVM/SAvagina; HSemen estimated by VSemen/SAvagina.