Being faithful

B, which stands in the original ‘ABC’ model for ‘Be faithful’, but also involves partner reduction as well as strict monogamy, has been called “The neglected middle child of ‘ABC’”.¹ It is difficult to gather evidence on whether HIV prevention programmes have influenced target populations in the direction of monogamy and reduction of the number of sexual partners, as there have been remarkably few co-ordinated campaigns and very little research.

This is to be regretted, because the rate of spread of HIV in a population is quite sensitively dependent on:

• the rate of partner change
• whether relationships are concurrent and consecutive
• whether partners are drawn from the local area or further afield.

The spread of HIV is crucially dependent on the establishment of sexual ‘networks’: remove a few links from those networks and the chain of infection can no longer be maintained. One 1998 paper commented: “Heterogeneity in sexual behaviour is vital to generate a high sexual activity ‘core group’ within which HIV spreads rapidly. How far out of this core group the virus will spread depends on the patterns of mixing within populations.”²

Another important aspect of reducing the rate of partner change is that it reduces the number of times people are likely to come across partners in early HIV infection. Phylogenetic testing indicates that anything from 10 to 50% of HIV infections may be transmitted by people in the first few months of HIV infection. High rates of partner change and especially of concurrent partnerships may be needed to establish the kind of ‘chain reaction’ that seeds high HIV prevalence in a population. Reducing partner numbers may have a seemingly disproportionate effect on reducing HIV incidence.

The association between HIV infection and both the number of partners you have and the number of partners your partners was presented by Daniel Halperin from the Harvard Center for Population and Development Studies.³

In the chart below, the percentage of people who have HIV in three African countries is very strongly associated with whether they have had one, two or at least three lifetime sexual partners:

In the second chart, HIV infection in one or both members of a couple is equally strongly associated with the reported faithfulness of the partners to each other. The likelihood of either the male or the female partner having HIV is strongly associated with their own reported faithfulness. (In this chart, the definition of ‘recent’ faithfulness is reporting having been exclusively monogamous for the past year.) Moreover, HIV infection is even more strongly associated with the reported exclusivity of the relationship, i.e. whether both partners are faithful to each other.

One problem with interventions into monogamy and reduction in the number of sexual partners is that it takes two people to be monogamous. An example of the traps the faithful partner of an unfaithful one can fall into is illustrated by a 2005 study⁴ which found that, among Afro-American heterosexual men and women, lower levels of condom use and contraception were found among people who agreed with the statement 'known partners are safe partners' than among ones who agreed that ‘trusted partners are safe partners'.