Elsevier

The Lancet

Volume 371, Issue 9631, 28 June–4 July 2008, Pages 2183-2191
The Lancet

Articles
New heterosexually transmitted HIV infections in married or cohabiting couples in urban Zambia and Rwanda: an analysis of survey and clinical data

https://doi.org/10.1016/S0140-6736(08)60953-8Get rights and content

Summary

Background

Sub-Saharan Africa has a high rate of HIV infection, most of which is attributable to heterosexual transmission. Few attempts have been made to assess the extent of HIV transmission within marriages, and HIV-prevention efforts remain focused on abstinence and non-marital sex. We aimed to estimate the proportion of heterosexual transmission of HIV which occurs within married or cohabiting couples in urban Zambia and Rwanda each year.

Methods

We used population-based data from Demographic and Health Surveys (DHS) on heterosexual behaviour in Zambia in 2001–02 and in Rwanda in 2005. We also used data on the HIV serostatus of married or cohabiting couples and non-cohabiting couples that was collected through a voluntary counselling and testing service for urban couples in Lusaka, in Zambia, and Kigali, in Rwanda. We estimated the probability that an individual would acquire an incident HIV infection from a cohabiting or non-cohabiting sexual partner, and then the proportion of total heterosexual HIV transmission which occurs within married or cohabiting couples in these settings each year.

Findings

We analysed DHS data from 1739 Zambian women, 540 Zambian men, 1176 Rwandan women, and 606 Rwandan men. Under our base model, we estimated that 55·1% to 92·7% of new heterosexually acquired HIV infections among adults in urban Zambia and Rwanda occurred within serodiscordant marital or cohabiting relationships, depending on the sex of the index partner and on location. Under our extended model, which incorporated the higher rates of reported condom use that we found with non-cohabiting partners, we estimated that 60·3% to 94·2% of new heterosexually acquired infections occurred within marriage or cohabitation. We estimated that an intervention for couples which reduced transmission in serodiscordant urban cohabiting couples from 20% to 7% every year could avert 35·7% to 60·3% of heterosexually transmitted HIV infections that would otherwise occur.

Interpretation

Since most heterosexual HIV transmission for both men and women in urban Zambia and Rwanda takes place within marriage or cohabitation, voluntary counselling and testing for couples should be promoted, as should other evidence-based interventions that target heterosexual couples.

Funding

US National Institute of Mental Health, National Institute of Child Health and Human Development, National Institute of Allergy and Infectious Diseases, Fogarty AIDS International Training and Research Program, Emory Center for AIDS Research, and the International AIDS Vaccine Initiative.

Introduction

Evidence suggests that a woman's greatest risk of contracting HIV lies within a marital relationship.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 Fewer attempts have been made to understand a man's risk within marriage;2, 12 but, in regions with generalised epidemics, high rates of serodiscordance among heterosexual couples in which the woman is HIV-positive suggest that a man's risk of marital HIV acquisition could also be substantial.2, 12, 13

Sub-Saharan Africa has the highest prevalence and incidence of HIV infection worldwide, mostly attributable to heterosexual transmission.14 Various studies have noted a high prevalence of HIV serodiscordance among heterosexual couples in Africa;15, 16, 17 population-based estimates of serodiscordance, from Demographic and Health Surveys (DHS), range from 2% (in Rwanda)13 to 13% (in Zimbabwe18 and Lesotho19). DHS data which show that between 45%18 and 75%20 of married HIV-positive individuals have HIV-negative spouses affirm the importance of HIV-prevention efforts for couples.18 Studies in Rwanda and Zambia with serodiscordant heterosexual couples showed that HIV transmission from HIV-positive to HIV-negative partners was 20–25% per year, irrespective of whether the man or woman was the positive partner.21, 22, 23 This rate accords with a coital frequency of two to three times per week and a risk of transmission on the order of one in 500 for each contact.23, 24, 25 Transmission in serodiscordant couples who have received joint voluntary counselling and testing ranges from 3% to 7% per year,21, 26, 27 with higher rates reported in cohorts that include a mixture of couples who know their own serostatus or that of their partner and those who don't.23, 25, 27 These data show that HIV-serodiscordant partnerships are a risky context for both women and men. These partnerships are also a potentially valuable context for preventive interventions.

We aimed to use both publicly available population-based data on sexual behaviour and service-based estimates of HIV serodiscordance to assess the proportion of heterosexually transmitted HIV infections in urban Zambia and urban Rwanda during a typical 12 month period which occur within the context of marital or cohabiting relationships. By quantifying the extent of HIV transmission among couples, we aimed to inform and perhaps to redirect the focus of HIV-intervention efforts, which have traditionally targeted individuals rather than couples.

Section snippets

Data sources

We used data collected by the Rwanda–Zambia HIV Research Group from July, 2003, to December, 2005, through voluntary counselling and testing services for couples in Kigali, Rwanda, and Lusaka, Zambia. Both partners were present at counselling sessions both before and after HIV tests, with simultaneous disclosure of results, results-specific counselling, training in the use of condoms, and referrals as appropriate for follow-up care.29 Data were available from 15 159 cohabiting couples and 8690

Results

In the DHS data for urban Zambia, 1739 (68·2%) women and 540 (78·4%) men reported sexual activity in the past 12 months, whereas in urban Rwanda, 1176 (45·0%) women and 606 (53·6%) men reported sexual activity in the past year (figure). The difference in sexual activity in the two areas is probably associated with the older average age of first sexual intercourse in Rwanda.13, 30, 31

Overall, 1388 (79·8%) of the sexually active Zambian women, 345 (63·9%) of the Zambian men, 997 (84·8%) of

Discussion

HIV prevalence in urban areas of Zambia in 2001 was 19·2% in men aged 15–59 and 26·3% in women aged 15–49.30 In 2005, urban HIV prevalence in Rwanda was 5·8% in men and 8·6% in women.13 Our most conservative model (model 1), predicted that most heterosexual HIV infections in both men and women in urban Zambia and Rwanda every year are probably transmitted within marriage. Our sensitivity analyses affirm the robustness of our key finding that most new heterosexually transmitted HIV infections in

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