Sexual transmission is considered to be the main source of the spread of the HIV/AIDS epidemic in Africa1.
The pervasive if unstated belief in the HIV/AIDS community is that males are primarily responsible for spreading the infection among married and cohabiting couples. A U.N. report entitled Women and HIV/AIDS: Confronting the Crisis reported: “Nearly universally, cultural expectations have encouraged men to have multiple partners, while women are expected to abstain or be faithful.” and “Faithfulness offers little protection to wives whose husbands have several partners or were infected before they were married.”
The evidence stems from the fact that most couples affected by HIV/AIDS in sub-Saharan Africa live in HIV-discordant or serodiscordant relationships, i.e. relationships in which only one of the two partners is HIV-positive while the other one is HIV-negative. Men are usually thought to be the partner who is HIV positive in most relationships, and most prevention campaigns are focused on men. A recent study fundamentally challenges the assumption that men are more likely to be the infected partner in a serodiscordant partnership.
The proportion of HIV-positive women in stable heterosexual serodiscordant relationships was 47% (95% CI 43-52) in 27 cohort studies enrolling 13,061 couples and 46% (CI 41-51) in Demographic and Health Survey data from 14 countries. Women are just as likely as men to be the HIV-positive partner in a discordant couple.
An earlier study from 5 African countries showed that in a sizeable proportion of HIV-infected couples only the woman is infected. The fraction of infected couples where only females are infected is between 30 and 40 percent; overall women are just as likely as men to be the HIV-positive partner in HIV-discordant partnerships.
These two sets of findings challenge the notion that males are the primary channel for HIV transmission from high-risk groups to the general population. They also contradict self-reports of sexual behavior by females. In the same surveys, during the last 12 months self-reported sexual intercourse outside the union among women in cohabiting couples ranges from 0.7 percent in Burkina Faso to 4.1 percent in Tanzania, and among cohabiting males from 8.7 percent in Burkina Faso to 25.9 percent in Cameroon. Substantial reporting biases in self-reported sexual behavior among men and women are common and have been documented.
Potential explanations for the sizeable portion of discordant couples where only the woman is infected, including polygyny (marriage to several wives), a bias in the coverage of the HIV testing in the survey, and earlier unions or infections before the current union. These explanations for the most part do not explain the data in these five countries.
In a sample limited to couples where the woman has been in only one union for 10 years or more —which should exclude most case of infections prior to the current union—the proportion of discordant female couples decreases, but only slightly, except in Ghana and Tanzania (table 2). The proportion of discordant female couples in Burkina Faso, Cameroon, and Kenya is still around a sizeable 30 percent of HIV-infected couples. The percentage of discordant female couples in Ghana and Tanzania decreases to 19.5 and 21.9 percent, respectively, which suggests that infection before marriage might explain some, but not all, of the cases of couples where only the woman is infected.
The proportion of discordant female couples is difficult to explain unless women are also sexually active outside the marriage (or cohabiting union).
Sexual intercourse among women outside the marriage (or cohabiting union) may be more common than reported. Or, even if infrequent, women may be more vulnerable to infection during these encounters, for example, because they are less likely to use condoms than single women and married men (a point I have documented in another study  co-authored with Rachel Kline).The point of this explanation is not to “blame” cohabiting women or suggest they are as “guilty” as cohabiting men in transmitting HIV/AIDS. The fact that sexual intercourse can, in many cases, be forced on women, should certainly be kept in mind.
Whatever its causes, sexual intercourse outside the union among women increases their vulnerability to HIV/AIDS. Designing prevention efforts for this population of women will not be an easy task given the culture of silence around women’s sexuality in many African countries and the stigma attached to those, and women in particular, with HIV/AIDS.
But to ignore the role that female sexual activity outside the union plays, among the other channels, in the transmission of the epidemic, would be a disservice to women.