It is obvious that the spread of any infection depends upon the contact patterns within the population which provide the route for transmission. In the case of HIV, the relevant contacts are sexual intercourse, sharing of injecting equipment among injecting drug users and, more rarely, using unscreened blood in transfusions and blood products, and repeated use of uncleaned medical equipment. The emergence of the HIV epidemic in the 1980s prompted the collection of interview data on patterns of sexual behaviour both in randomly sampled household based surveys1,2,3
and in convenience samples of particular high risk groups.4
Contact tracing studies identified the network of sexual contacts between men who have sex with men who were early cases of AIDS.5
Subsequently, case–control and cohort studies identified sexual contact and injecting drug use as the main routes of transmission of HIV. In 1988, the World Health Organization (WHO) Global Program on AIDS estimated that heterosexual transmission accounted for 80% of HIV infections in Africa.6
Although the estimate of the contribution of heterosexual transmission in Africa has been disputed by some authors,7
there is consensus that sexual transmission of HIV is the main mode (over 95%) of transmission for HIV infection among adults in Africa.8
Over time, methods have been developed to evaluate and improve the validity of self‐reported sexual behaviours and to measure the most relevant behaviours. However, there are often trade‐offs between collecting simple, comparable, and consistent indicators of risk behaviour and developing a detailed and truthful description of the range of behaviours within populations.
From early in the AIDS pandemic HIV sentinel surveillance has been recommended by WHO.9
More recently the Joint United Nations Programme on AIDS (UNAIDS)/WHO HIV surveillance working group, in collaboration with other international partners, has updated its recommendations and advocated the implementation of “second generation surveillance”.10
One of the key features of this strategy is to continue monitoring both sexual behaviour and patterns of prevalence of other sexually transmitted diseases, in the expectation that these will assist in understanding the spread of HIV.10
However, the difficulties inherent in collecting reliable and valid data on sexual behaviour and patterns of incidence of sexually transmitted diseases, and in understanding their relevance for HIV risk have discouraged many programmes from collecting or using such data.
Here, we review the reasons for collecting such data, describe some of the difficulties in interpreting trends in risk behaviour, and identify the potential uses of such surveillance data. As in the rest of this supplement, our focus is on the behaviours of populations where there is a generalised heterosexual epidemic.