Partner Acquisition Research Articles

Bridge populations in the spread of HIV/AIDS in Thailand.

To determine the extent to which men provide a bridge population between commercial sex workers (CSW) and the general female population in Thailand. Sexual network and serological data were collected from a systematic quota sample of low income men and truckers during 1992 in three Thailand provinces. Completed sample size was 1075 men aged 17-45 years and 330 truckers. Sexual network information was used to identify those men who have sex with both female CSW and non-CSW partners (the 'bridge population'). A new method was used for calculating the partner acquisition rate and to establish the potential number of women exposed to HIV via inconsistent condom use among the bridge population. Approximately 17% of men and 25% of truckers can be included in the bridge population. These men are more likely to be HIV-positive and to have had at least one other sexually transmitted infection in the past year (odds ratio, 2.2 and 3.4, respectively). Consistent condom use with CSW is less than 30%, and is less than 1% with non-CSW partners. As a result, 30 women in the general population were potentially exposed to HIV per 100 sexually active men in the last year:nine women each additional year. Younger men and truckers expose almost twice as many women to HIV; more female peers than wives are exposed. Bridge populations may be as important as "core groups' for the spread of HIV into the general Thai population. Young men and women are strategic intervention targets because they have more partners, are more likely to be in bridging networks, and are more receptive to condom use.

The evolution of virulence in sexually transmitted HIV/AIDS

A mathematical model is used to examine the effects of host population demography and transmission behavior on the evolution of virulence of a sexually transmitted pathogen such as HIV. The effect of the rate at which hosts acquire new partners is shown to depend critically on the details of the host population's growth pattern, sexual contact rate, and level of infection. At density-limited equilibrium, new partner acquisition rates have no effect on virulence. In an exponentially growing host population, higher partner acquisition rates favor the less virulent strain, as do lower rates of host population growth. In contrast, in uninfected populations, faster new partner acquisition rates encourage epidemics of the more virulent strain. Two extensions of the model--one including vertical transmission and another including within-host evolution--confirm the robustness of the predictions.

Balancing sexual partnerships in an age and activity stratified model of HIV transmission in heterosexual populations.

A mathematical model of the transmission dynamics of HIV-1 in a heterosexual population stratified by age, sex, and sexual activity (defined by rates of sexual partner acquisition) is presented. The model represents an extension of previous studies with a special focus on patterns of mixing or contact between sexual activity and different age classes of the two sexes. A range of mixing patterns between these groups is specified for both sexes. Mixing is described on two scales from fully assortative to fully disassortative, with random defined either according to numbers of sexual partnerships or numbers of people. The sexual partnerships in the model are balanced by changes in the rates of sexual partner acquisition between particular groups and a range of changes, from only women changing behaviour to only men changing behaviour, are analysed. The pattern of mixing is most influential in determining the shape and magnitude of the epidemic, but the manner in which people choose partners (i.e. dependent on numbers or proportions in the population) is also important. The relative importance of variation in transmission probabilities and mean rates of partner change on the course of the HIV epidemic is also illustrated. The analysis of the sensitivity of predictions to changing parameters in the force of infection term of the model provides a theoretical basis from which the influence of control strategies and the demographic effects of HIV can be analysed.

Sexual Self-Defense Versus the Liaison Dangereuse: A Strategy for AIDS Prevention in the ’90s

The present public health strategy to encourage the adoption of "safe sex" practices to contain the AIDS epidemic in America is incomplete. Current policy is responsive to and appropriate for control of homosexual, but not heterosexual transmission. Powerful societal forces restrict a woman's perception of risk. Consequently, the adoption of safe sex (condom use/insistence on use) by women at risk has not matched safe sex practice by homosexual men. Predictably, pattern two (heterosexual, maternal-fetal) HIV transmission is now rapidly increasing in the United States, particularly among minority women. In anticipation of an intensified pattern two subepidemic, AIDS containment policy should be reoriented to develop the role of women in AIDS prevention. An initiative, termed "sexual self-defense" (SSD), combines the technology of double-barrier (female irrespective of male) protection with a "universal precautions" approach to long-term sexual risk management. The initiative addresses both per-contact infectiousness and new partner acquisition, the principal determinants of HIV spread. As a female-targeted strategy, SSD is a timely supplement to existing programs, consistent with the direction of contemporary women's movements in the United States. A "street smart" approach, SSD bridges ethnic and socioeconomic individual differences. As a unifying philosophy of risk management in health promotion, SSD may avert the threatened fragmentation of AIDS control from existing programs of sexually transmitted disease control and teenage pregnancy prevention.