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HIV/AIDS, Rape and Conflict: Predictions Based on Mathematical Modelling

Rape during wartime greatly increases an individual’s risk of contracting HIV, according to predictions comparing conflict and non-conflict settings. Dr Anna Foss, of the London School of Hygiene and Tropical Medicine (LSHTM), explained the estimates and their underlying assumptions at a seminar on 4 December.

She set out how rape-induced genital injury increases the likelihood of being infected by HIV and how a sex industry, at times including peacekeepers, arises out of conflict. Foss showed how forced and transactional sex within a range of scenarios could lead to higher rates of HIV transmission (especially in the case of anal rape by a gang).The event, called HIV/AIDS and Rape: Modelling Predictions of the Increase in Individual Risk of HIV Infection from Forced Sex, was held at LSHTM. It was part of a series of seminars to mark  16 Days of Activism Against Gender Violence (25 November - 10 December). The models and predictions discussed were based on work conducted by LSHTM’s Gender Violence and Health Centre and LSHTM’s HIV Tools Research Group.

Conflict situations
Foss, a Lecturer in Mathematical Modelling, began by explaining how a high proportion of the population experience forced sex in a conflict or post-conflict setting. This contributes to higher HIV transmission than consensual sex in peacetime in two ways. Firstly, rape is associated with violence and is more likely to cause genital injury. Foss highlighted how trauma centre figures show that 36-53 per cent of raped women suffer genital injuries. Such injuries increases a woman’s susceptibility to contracting HIV because they damage the epithelium – the lining of the reproductive tract which acts as a natural barrier against infection. Secondly, Foss said there is likely to be a higher level of HIV prevalence among perpetrators of forced sex in conflict settings, since some of the risk factors for HIV are common also to the risk factors for violence.

<span style="FONT-SIZE:" 10pt;="" font-family:="" 'arial','sans-serif'"="">Scenarios and assumptions
During the seminar various conflict and non-conflict scenarios were set out, thereby showing the increased relative risk of HIV transmission in conflict settings. These included:
Conflict scenario Comparison
Risk ratio
Adult female forced to have sex by unknown combatant assailants (multiple site trauma) Same number of consensual sex acts with one partner from own community   4.3
Adult female raped by 3 men at refugee camp (multiple site trauma) and also has low risk male partner with whom she has 3 consensual sex acts Only has 3 consensual sex acts with low risk male partner   5.3
Adult female trades sex with several male members of peacekeeping force (single site trauma once in every 8 sex acts) Same number of consensual sex acts with one man from own community   1.5
Anal rape of adult male or female by 3 men at refugee camp, and also has low risk partner of opposite sex with whom he/she has 3 consensual penile-vaginal sex acts Only has 3 consensual penile-vaginal sex acts with low risk partner   86


Other scenarios were also considered, including the potential impact of refugee movements. The models show how the arrival of a higher HIV prevalence group would increase HIV transmission by a multiplicative factor of 1.4 and the arrival of a lower HIV prevalence group would decrease HIV transmission by a multiplicative factor of 0.6.

Foss also referred to the limitations of such modelling because of limited quantitative data on patterns of HIV and STIs and coercion in conflict settings. Moreover, she stressed that although the scenarios are considered to be “typical”, they are still hypothetical.

The models were based on a series of assumptions:

  • The probability of male to female HIV transmission was 1 in 500 per sex act.
  • Genital trauma increases the per-sex-act risk by a factor of 1.5 for a single site and by 3 for multiple sites, and by 6 for anal rape or child sexual abuse.
  • The likelihood of HIV being transmitted per-sex-act by anal sex is 10 times higher than vaginal sex.
  • HIV and STI prevalence twice as high among higher risk / violent males vs other males.
  • STIs increase probability of HIV transmission threefold.
  • Five per cent of those infected with HIV would have a high viral load having just acquired HIV, and, in these cases, the likelihood of transmission would be increased tenfold.

Implications of the models
Foss’ presentation focused on an individual’s risk of contracting HIV in conflict settings, rather than the population-level prevalence approach adopted by UNHCR’s Paul Spiegel at the 17th International AIDS Conference in Mexico this August. She showed how there is an increased risk of HIV transmission during wartime because of the higher incidence of forced sex and accompanying HIV transmission co-factors, including genital injury. Foss added: “Rape and coercion should be considered in HIV programmes. Post-rape services should be offered, as well as referral to HIV testing and counselling”.

By Guy Collender, Communications Officer, LIDC

Acknowledgements and Further


Dr Anna Foss carried out the work with Rachel von Simson, former LSHTM student, and LSHTM staff Professor Charlotte Watts, Dr Cathy Zimmerman and Mazeda Hossain. The project was supported by the AIDS, Security & Conflict Initiative, convened by the Netherlands Institute of International Relations ‘Clingendael’ and the Social Science Research Council. Partial funding also came from the Sigrid Rausing Trust.

Foss and Watts are also members of LSHTM's DFID-funded Research Programme Consortium for Research and CapacityBuilding in Sexual and Reproductive Health and HIV in Developing Countries.