Modelling the interactions between herpes simplex virus type 2 and HIV: implications for the HIV epidemic in southern India.
BACKGROUND
The role of herpes simplex virus type 2 (HSV-2) in the HIV epidemic and the potential impact of HSV-2 suppressive therapy have previously been explored only within the context of sub-Saharan Africa. In this analysis, modelling is used to estimate the contribution of HSV-2 to HIV transmission from clients to female sex workers (FSW) in a southern Indian setting and the maximum potential impact of 'perfect' HSV-2 suppressive therapy on HIV incidence.


METHODS
A dynamic HSV-2/HIV model was developed, parameterised and fitted to Mysore data. The model estimated the attributable fractions of HIV infections due to HSV-2. Multivariate sensitivity analyses and regression analyses were conducted.


RESULTS
The model suggests that 36% (95% CI 22% to 62%) of FSW HIV infections were due to HSV-2, mostly through HSV-2 asymptomatic shedding. Even if HSV-2 suppressive therapy could eliminate the effect of HSV-2 on HIV infectivity among all co-infected clients, only 15% (95% CI 3% to 41%) of HIV infections among FSW would have been averted. 36% (95% CI 18% to 61%) of HIV infections among HSV-2-infected FSW could have been averted if suppressive therapy reduced their risk of HIV acquisition to that of HSV-2-uninfected FSW.


CONCLUSIONS
HSV-2 contributes substantially to HIV in this southern Indian context. However, even in the best case scenario, HSV-2 suppressive therapy is unlikely to reduce HIV transmission or acquisition by more than 50% (as aimed for in recent trials), because of the limited strength of the interaction effect between HSV-2 and HIV.
Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, 15-17 Tavistock Place, London WC1H 9SH, UK. anna.foss@lshtm.ac.uk
Anna M
AM
Foss
Peter T
PT
Vickerman
Philippe
P
Mayaud
Helen A
HA
Weiss
B M
BM
Ramesh
Sushena
S
Reza-Paul
Reynold
R
Washington
James
J
Blanchard
Stephen
S
Moses
Catherine M
CM
Lowndes
Michel
M
Alary
Charlotte H
CH
Watts
D058872:Epidemics / Q000706:statistics & numerical data*; D005260:Female; D015658:HIV Infections / Q000150:complications / Q000453:epidemiology* / Q000635:transmission; D006558:Herpes Genitalis / Q000150:complications / Q000453:epidemiology*; D018258:Herpesvirus 2, Human; D006801:Humans; D007194:India / Q000453:epidemiology; D015233:Models, Statistical; D012044:Regression Analysis; D011477:Sex Work; D017201:Virus Shedding