Who mixes with whom among men who have sex with men? Implications for modelling the HIV epidemic in southern India
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Author(s)
Type
Journal Article
Abstract
In India, the identity of men who have sex with men (MSM) is closely related to the role taken in anal sex
(insertive, receptive or both), but little is known about sexual mixing between identity groups. Both role
segregation (taking only the insertive or receptive role) and the extent of assortative (within-group)
mixing are known to affect HIV epidemic size in other settings and populations. This study explores how
different possible mixing scenarios, consistent with behavioural data collected in Bangalore, south India,
affect both the HIV epidemic, and the impact of a targeted intervention. Deterministic models describing
HIV transmission between three MSM identity groups (mostly insertive Panthis/Bisexuals, mostly
receptive Kothis/Hijras and versatile Double Deckers), were parameterised with behavioural data from
Bangalore. We extended previous models of MSM role segregation to allow each of the identity groups to
have both insertive and receptive acts, in differing ratios, in line with field data. The models were used to
explore four different mixing scenarios ranging from assortative (maximising within-group mixing) to
disassortative (minimising within-group mixing). A simple model was used to obtain insights into the
relationship between the degree of within-group mixing, R0 and equilibrium HIV prevalence under
different mixing scenarios. A more complex, extended version of the model was used to compare the predicted HIV prevalence trends and impact of an HIV intervention when fitted to data from Bangalore.
With the simple model, mixing scenarios with increased amounts of assortative (within-group) mixing
tended to give rise to a higher R0 and increased the likelihood that an epidemic would occur. When the
complex model was fit to HIV prevalence data, large differences in the level of assortative mixing were
seen between the fits identified using different mixing scenarios, but little difference was projected in
future HIV prevalence trends. An oral pre-exposure prophylaxis (PrEP) intervention was modelled,
targeted at the different identity groups. For intervention strategies targeting the receptive or receptive
and versatile MSM together, the overall impact was very similar for different mixing patterns. However,
for PrEP scenarios targeting insertive or versatile MSM alone, the overall impact varied considerably for
different mixing scenarios; more impact was achieved with greater levels of disassortative mixing.
(insertive, receptive or both), but little is known about sexual mixing between identity groups. Both role
segregation (taking only the insertive or receptive role) and the extent of assortative (within-group)
mixing are known to affect HIV epidemic size in other settings and populations. This study explores how
different possible mixing scenarios, consistent with behavioural data collected in Bangalore, south India,
affect both the HIV epidemic, and the impact of a targeted intervention. Deterministic models describing
HIV transmission between three MSM identity groups (mostly insertive Panthis/Bisexuals, mostly
receptive Kothis/Hijras and versatile Double Deckers), were parameterised with behavioural data from
Bangalore. We extended previous models of MSM role segregation to allow each of the identity groups to
have both insertive and receptive acts, in differing ratios, in line with field data. The models were used to
explore four different mixing scenarios ranging from assortative (maximising within-group mixing) to
disassortative (minimising within-group mixing). A simple model was used to obtain insights into the
relationship between the degree of within-group mixing, R0 and equilibrium HIV prevalence under
different mixing scenarios. A more complex, extended version of the model was used to compare the predicted HIV prevalence trends and impact of an HIV intervention when fitted to data from Bangalore.
With the simple model, mixing scenarios with increased amounts of assortative (within-group) mixing
tended to give rise to a higher R0 and increased the likelihood that an epidemic would occur. When the
complex model was fit to HIV prevalence data, large differences in the level of assortative mixing were
seen between the fits identified using different mixing scenarios, but little difference was projected in
future HIV prevalence trends. An oral pre-exposure prophylaxis (PrEP) intervention was modelled,
targeted at the different identity groups. For intervention strategies targeting the receptive or receptive
and versatile MSM together, the overall impact was very similar for different mixing patterns. However,
for PrEP scenarios targeting insertive or versatile MSM alone, the overall impact varied considerably for
different mixing scenarios; more impact was achieved with greater levels of disassortative mixing.
Date Issued
2014-08-21
Date Acceptance
2014-04-02
Citation
Journal of Theoretical Biology, 2014, 355, pp.140-150
ISSN
1095-8541
Publisher
Elsevier
Start Page
140
End Page
150
Journal / Book Title
Journal of Theoretical Biology
Volume
355
Copyright Statement
© 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/3.0/).
(http://creativecommons.org/licenses/by/3.0/).
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Subjects
Science & Technology
Life Sciences & Biomedicine
Biology
Mathematical & Computational Biology
Life Sciences & Biomedicine - Other Topics
BIOLOGY
MATHEMATICAL & COMPUTATIONAL BIOLOGY
Mathematical model
Mixing matrix
Sexually transmitted infection
Disassortative mixing
Pre-exposure prophylaxis
HOMOSEXUAL ROLE SEPARATION
SEXUALLY-TRANSMITTED INFECTIONS
DISEASE TRANSMISSION
SPREAD
PREVENTION
AIDS
POPULATIONS
PREVALENCE
PATTERNS
BEHAVIOR
Publication Status
Published