Introduction:
Understanding the impact of past interventions and
how it affected transmission
dynamics is key to guiding prevention efforts. We e
stimated the population-level impact of
condom, antiretroviral therapy (ART), and preventio
n of mother-to-child transmission activities
on HIV transmission and the contribution of key ris
k factors on HIV acquisition and
transmission.
Methods:
An age stratified dynamical model of sexual and ve
rtical HIV transmission among the
general population, female sex workers (FSW), and m
en who have sex with men (MSM) was
calibrated to detailed prevalence and intervention
data. We estimated the fraction of HIV
infections averted by the interventions, and the fr
action of incident infections acquired and
transmitted by different populations over successiv
e 10-year periods (1976-2015).
Results:
Overall, condom use averted 61% (95% Credible Inte
rvals: 56-66%) of all adult
infections during 1987-2015 mainly due to increases
by FSW (46% of infections averted). In
comparison, ART prevented 15% (10-19%) of adult inf
ections during 2010- 2015. As a result,
FSW initially (1976-1985) contributed 95% (91-97%)
of all new infections, declining to 19%
(11-27%) during 2005-2015. Older men and clients mi
xing with non-FSW are currently the
highest contributor to transmission. MSM contribute
d
≤
4% transmissions throughout. Young
women (15-24 years; excluding FSW) do not transmit
more infection than they acquired.
Conclusion:
Early increases in condom use, mainly by FSW, have
substantially reduced HIV
transmission. Clients of FSW and older men have bec
ome the main source of transmission
whereas young women remain at increased risk. Stren
gthening prevention and scaling-up of
ART, particularly to FSW and CFSW, is important.