Table 1

Parameter values for the Cotonou scenario

ParametersValuesSymbols in equations*Source of data
*See the appendix.
CSW, commercial sex worker; Gc, gonorrhoea.
Biological parameters
Duration of HIV infection(19–22)
    Phase 16 monthsγ1
    Phase 26.25 yearsγ2
    Phase 32 yearsγ3
    Full blown AIDS1 yearα
HIV transmission probability per partnership in a circumcised populationin phase 1,phase 2,phase 3(19–28)
Female to male
    Low to low15.00%,3.45%,7.50%βnew11,1,1βnew21,1,1βnew31,1,1
    Low to high11.50%,2.65%,5.00%βnew11,1,2βnew21,1,2βnew31,1,2
    High to low0.65%,0.15%,0.27%βnew11,2,1βnew21,2,1βnew31,2,1
    High to high0.65%,0.15%,0.27%βnew11,2,2βnew21,2,2βnew31,2,2
Male to female
    Low to low30.00%,6.90%,13.00%βnew12,1,1βnew22,1,1βnew32,1,1
    Low to high1.30%,0.30%,0.54%βnew12,1,2βnew22,1,2βnew32,1,2
    High to low23.00%,5.30%,10.00%βnew12,2,1βnew22,2,1βnew32,2,1
    High to high1.30%,0.30%,0.54%βnew12,2,2βnew22,2,2βnew32,2,2
Relative risk of HIV if not circumcised2RRHIV/non-circ(29–34)
Proportion of men circumcised100%(12–14)
Relative risk of HIV infection if HIV negative or partner is infected with Gc3RRHIV/Gc(35, 36)
First HIV cases (seed) in 19802 in low activity classes andX1011(1980)=1, X1021(1980)=1(12, 13)
3 in high activity classesX1012(1980)=2, X1022(1980)=1
STD modelled GonorrhoeaGc(14)
Duration of infection with Gc(14–16, 37, 38)
    Female low5.7 months1/σ11
    Female high (CSW)1.3 months1/σ12
    Male low3.3 months1/σ21
    Male high (frequent clients)1.3 months1/σ22
Gc transmission probability per partnershipFemale to maleMale to female(37–41)
    Low to low0.600.95ψnew111ψnew211
    Low to high0.450.42ψnew112ψnew212
    High to low0.220.8ψnew121ψnew221
    High to high0.220.42ψnew122ψnew222
Demographic parameters
Total population size122 605 females and 115 558 males in 1980; 205 380 and 200 003 in 1997hs,i Xhski(t) for i=1,2, k=1,2, h=0,4, s=0,1(13, 14, 42–44)
Growth rate of the populationIncreases from 2.5% in 1980 to 4.3% in 1997 and eventually plateaus at 3.8% in absence of AIDSΛki (t)(14, 16, 42–44)
Size of the CSW1.2%sX0s12(1980)/ ∑s,i X0s1i(1980), s=0,1, i=1,2(13, 17)
Size of client population12.0%sX0s22(1980)/ ∑s,i X0s2i(1980), s=0,1, i=1,2(13, 14, 17)
Renewal of the CSWAbout 2% in 1997 but increases as more CSW get infected and progress to AIDS (details in appendix)50% of the CSW who progress to AIDS are replaced by HIV negative with STD status according to Gc prevalence.(14, 16, 45)
R0012(t)=R0s12(t) =0.5•γ3•X123s(t), s=0,1
Sexual life expectancy45.5 years1/μ(14, 16, 42–44)
Sexual behaviour
Condom use at baseline50% of CSW partnerships with men are protected by condomsCond1,2,1% (1980)(14, 16, 17)
Cond1,2,2% (1980)
From T1 = 1980 onwardCond2,1,2% (1980)
No screeningCond2,2,2% (1980)
Annual rates of new partners acquisition at baseline(12, 14, 16–17)
    Low risk females1.5m11(1980)
    Low risk males1.7m21(1980)
Mixing patternVery assortative(14, 16)
Female with maleMale with female
    High with low5.3%4.9%ρ121(1980)ρ221(1980)
    High with high94.7%95.1%ρ122(1980)ρ222(1980)
    Low with low86.0%85.1%ρ111(1980)ρ211(1980)
    Low with high14.0%14.9%ρ112(1980)ρ212(1980)