Younger age, recent HIV diagnosis, no welfare support and no annual sexually transmissible infection screening are associated with nonuse of antiretroviral therapy among HIV-positive gay men in Australia.

OBJECTIVES: With the increasing momentum to maximize the benefits of antiretroviral therapy (ART), better understanding of opportunities and challenges in increasing ART coverage and promoting early ART initiation is urgently needed. Key sociodemographic, clinical and behavioural factors associated with Australian HIV-positive gay men's current nonuse of ART were systematically examined. METHODS: Data were based on 1911 responses from HIV-positive men who had participated in the Australian Gay Community Periodic Surveys (GCPS) between 2010 and 2012. Stratified univariate analysis and multivariate logistic regression were used. RESULTS: A majority of the participants were recruited from gay community venues and events and self-identified as gay or homosexual. On average, they were 44 years old and had been living with HIV for at least 10 years. Close to 80% (n=1555) were taking ART, with >90% further reporting an undetectable viral load at the time of the survey. From 2010 to 2012, there had been a moderate increase in ART uptake [adjusted odds ratio (AOR) 1.40; 95% confidence interval (CI) 1.20-1.65]. In addition, younger age (AOR 1.66; 95% CI 1.45-1.92), recent HIV diagnosis (AOR 1.78; 95% CI 1.59-1.98), not receiving any social welfare payments (AOR 2.20; 95% CI 1.05-2.54) and no annual screening for sexually transmissible infections (AOR 1.55; 95% CI 1.03-2.34) were independently associated with ART nonuse. CONCLUSIONS: Current ART coverage among HIV-positive gay men in Australia is reasonably high. To further increase ART coverage and promote early ART initiation in this population, better clinical care and sustained structural support are needed for HIV management throughout their life course.

HIV testing, gay community involvement and internet use: social and behavioural correlates of HIV testing among Australian men who have sex with men.

A significant minority of Australian men who have sex with men (MSM) have never been tested for HIV and many men do not test as often as recommended. Using data from 1770 HIV-negative and untested MSM collected in a national, online survey, we compared men who had never tested for HIV with those who had tested over 12 months ago and men who had tested over 12 months ago with those that had tested in the past year. Two multivariate logistic regression models were constructed. Compared with men tested over 12 months ago, untested men were younger, less educated, less likely to have unprotected anal intercourse with a regular male partner, less likely to have sought advice from a doctor, nurse or community organisation, more likely to expect HIV-negative disclosure, had fewer gay friends and spent more time using social networking websites. Compared with men who had tested over 12 months ago, men who had tested within the last year were younger, more likely to expect HIV-negative disclosure and disclose to casual partners, more likely to have sought advice from a doctor or nurse, had attended gay pools, gyms or beaches and had more gay friends and more male sex partners. Our findings suggest that the Internet and sex education in schools are important ways to promote HIV testing to untested MSM. Testing reinforcement messages delivered through gay community outreach and primary care will reach previously tested MSM.

Predictors of HIV disclosure among untested, HIV-negative and HIV-positive Australian men who had anal intercourse with their most recent casual male sex partner.

We analysed HIV disclosure between Australian men who have sex with men (MSM) who reported anal intercourse with their last casual male partner. Of 804 MSM included in the analysis, 413 reported HIV disclosure and 391 reported no disclosure. After identifying bivariate associations with HIV disclosure, we developed three models of HIV disclosure (one for untested, one for HIV-negative and one for HIV-positive MSM). A range of factors was found to be associated with HIV disclosure. Having previously had sex with the last casual male partner and expecting HIV-negative and HIV-positive men to disclose before sex were predictors of HIV disclosure shared by more than one serostatus group. As unprotected anal intercourse was more common among MSM who disclosed (across all serostatus groups), we suggest caution should be exercised before encouraging HIV disclosure as a prevention strategy. Nondisclosure remains more strongly associated with safe sex among Australian MSM.

Defining high HIV incidence subgroups of Australian homosexual men: implications for conducting HIV prevention trials in low HIV prevalence settings.

OBJECTIVES: The aim of the study was to assess whether subpopulations with sufficiently high HIV incidences for HIV prevention trials can be identified in low HIV incidence settings such as Australia. METHODS: In a community-based cohort study of HIV-negative homosexually active men in Sydney, Australia, potential risk factors associated with an annual HIV incidence of ≥2 per 100 person-years (PY) were identified. A stepwise procedure ranked these factors according to HIV incidence, to create a 'high-incidence' subgroup of participants. Willingness to participate in HIV prevention trials was assessed. RESULTS: Although the incidence in the cohort overall was only 0.78 per 100 PY, nine risk variables were associated with an HIV incidence of 2 per 100 PY or greater. Stepwise inclusion of these variables revealed a 'high-incidence' subgroup of men representing 24% of the total follow-up time with a combined HIV incidence of 2.71 per 100 PY, who reported at least one of three risk factors in the past 6 months. These men were more willing than others to participate in vaccine and antiretroviral therapy HIV prevention trials. CONCLUSIONS: These findings demonstrate that it is possible to identify high HIV incidence subpopulations in low-incidence settings such as Australia, and these men are of above average willingness to participate in HIV prevention trials.

Enhancing HIV prevention requires addressing the complex relationship between prevention and treatment.

Globally each year, HIV continues to infect millions of people, and the number of people living with HIV and AIDS grows. While there has been an increase in funding for HIV and AIDS, there is a growing gap between the funds available and the funds needed for both prevention and treatment. Yet, one of the means of closing that gap - preventing new infections - has slipped down the agenda. In arguing for a significant intensification of the HIV prevention response, and the relevance of a strong social stance within this response, this paper addresses the need to manage finding a balance between prevention and treatment and care. Not only is there not enough being spent on HIV prevention, but also in some instances, the prevention agenda has been hijacked by those who favour morally conservative, but ineffective, HIV prevention strategies. We argue that effective prevention needs to be firmly located within the everyday realities affecting communities and societies, and needs to focus on what is known to work. In particular, we need to move beyond a public health underpinned by neo-liberal notions of agency and individual responsibility to a public health that recognises the collective nature of epidemics, and works with communities and networks to transform social relations. This latter, more 'social' public health, is concerned with the social, political and economic factors that produce HIV risk and responses to it. Contrary to what some might suggest, HIV prevention has not failed, rather, governments and donors have failed HIV prevention.

Prevalence, incidence and risk factors for pharyngeal chlamydia in the community based Health in Men (HIM) cohort of homosexual men in Sydney, Australia.

OBJECTIVES: To determine the prevalence, incidence and risk factors for pharyngeal Chlamydia trachomatis in the community based Health in Men (HIM) cohort of HIV negative homosexual men in Sydney, Australia. METHODS: From January 2003, all HIM participants were offered annual screening for pharyngeal chlamydia using BD ProbeTec nucleic acid amplification testing (NAAT). Detailed sexual behavioural data were collected every 6 months, and risk factors for infection and hazard ratios were calculated using Cox regression. RESULTS: Among 1427 participants enrolled, the prevalence of pharyngeal chlamydia on initial testing was 1.06% and the incidence rate was 0.58 per 100 person-years. More than 50% of all infections were identified on baseline testing and 68% of men with pharyngeal infection had no evidence of concurrent anogenital chlamydia. There was no association of pharyngeal chlamydia with sore throat. Infection was significantly associated with increasing frequency of receptive penile-oral sex with ejaculation with casual partners (p = 0.009), although approximately half of infections occurred in participants not reporting this risk behaviour. Neither kissing nor oro-anal practices were associated with infection. CONCLUSION: The incidence of pharyngeal chlamydia infection in the HIM study was relatively low; however, the relatively high prevalence on baseline testing compared to incidence suggests a long duration of infection. Occasional screening for pharyngeal chlamydia in homosexual men who frequently practise receptive oral sex with ejaculation may be warranted.

Sex work and risk behaviour among HIV-negative gay men.

Gay men who engage in sex work may be at increased risk through risk behaviour outside the context of sex work. Among participants in the Health in Men (HIM) cohort of HIV-seronegative gay men in Sydney, 19.7% had ever engaged in sex work. Five percent reported being paid for sex in a six-month period during the study (2001-2006); a minority (18.3%) of these current sex workers reported unprotected anal intercourse (UAI) with clients and 62.0% reported UAI with any casual partners. The practice of sex work itself may not represent increased risk for HIV transmission but sex workers in this study were, nonetheless, at markedly increased risk in other aspects of their lives.

Differences between HIV-positive gay men who 'frequently', 'sometimes' or 'never' engage in unprotected anal intercourse with serononconcordant casual partners: positive Health cohort, Australia.

By measuring the actual number of risk acts engaged in by HIV-positive men participating in the Positive Health (PH) cohort study, this paper sets out to document the distribution of risk acts, to report on the proportion of acts of unprotected anal intercourse with casual (UAIC) partners that occurred between HIV-positive men (i.e. seroconcordant positive) and to examine the factors that differentiated men who 'frequently' compared with 'sometimes' or 'never' engaged in unsafe UAIC (i.e. UAIC with serononconcordant partners: partners who have not tested positive for HIV). The findings show that 42.6% of all UAIC acts occurred between seroconcordant HIV-positive partners, posing no risk of HIV infection to an HIV-negative person. A minority of participants (10%) accounted for the majority (70.7%) of the unsafe acts of UAIC. The HIV-positive men who 'sometimes' engaged in unsafe UAIC had higher treatment optimism scores and were more likely to use Viagra in comparison with those who did not engage in such risk. Those who reported 'frequent' engagement in unsafe UAIC were more likely to engage in a range of esoteric sexual practices, be slightly less well educated and be taking antiretroviral therapy compared with HIV-positive men who 'sometimes' engaged in unsafe UAIC. As such, taking ART but not viral load, predicted frequent unsafe UAIC. When considered alongside earlier studies, these results suggest that HIV-negative men who engage in esoteric sexual practices may be at increased risk of HIV transmission, not necessarily because they engage in esoteric sex practices but because of the sub-cultural milieu in which esoteric sex is occurring. The findings from this study also endorse the measurement of UAIC acts as a useful gauge of risk.

Marijuana as therapy for people living with HIV/AIDS: social and health aspects.

Therapeutic use of marijuana has emerged as an important issue for people living with cancer, HIV/AIDS and multiple sclerosis. This paper examines therapeutic use of marijuana in the Positive Health cohort study, a longitudinal cohort study of men and women living with HIV/AIDS in NSW and Victoria, Australia. Factors that distinguish therapeutic use of marijuana from recreational use were assessed by comparisons on a range of social and health-related variables. The results show that among 408 participants, 59.8% reported some use of marijuana in the past six months. Of those participants (n=244), 55.7% reported recreational use only of marijuana and 44.3% report mixed use of marijuana for therapeutic and recreational purposes. Multivariate logistic regression analysis showed that participants who used marijuana for therapeutic purposes were significantly more likely than recreational-only users to have used other complementary or alternative therapies, experienced HIV/AIDS-related illness or other illnesses in the past 12 months, had higher CD4/T-cell counts, had lower incomes, be younger in age and less likely to have had a casual partner in the six months prior to interview. These results show that a substantial proportion of people living with HIV/AIDS (PLWHA) use marijuana for therapeutic purposes, despite considerable legal barriers, suggesting marijuana represents another option in their health management. Rather than solely using marijuana in response to illness, the experience of illness may influence a person's understanding of their marijuana use, so that they come to understand it as therapeutic. Further research might consider possible interactions between cannabinoids and antiretroviral treatments, potential use of oral THC and the difficulties faced by clinicians and PLWHA in discussing marijuana in the current legal context.

Incidence and risk factors for urethral and anal gonorrhoea and chlamydia in a cohort of HIV-negative homosexual men: the Health in Men Study.

BACKGROUND: Early detection and treatment of bacterial sexually transmitted infections has been advocated as an HIV prevention strategy. AIM: To inform screening guidelines, the incidence and risk factors for urethral and anal gonorrhoea and chlamydia were studied in a prospective cohort of community-based HIV negative homosexual men in Sydney, New South Wales, Australia. METHODS: All participants were offered annual screening for gonorrhoea and chlamydia (study-visit diagnoses) on urine and anal swabs using nucleic acid amplification. Participants also reported diagnoses of gonorrhoea and chlamydia made elsewhere between interviews (interval diagnoses). All diagnoses were summed to create a combined incidence rate, and detailed data on specific sexual practices with casual and regular partners were collected. RESULTS: Among 1427 men enrolled, the combined incidence rates were 3.49 and 2.96 per 100 person-years for urethral and anal gonorrhoea, respectively; and 7.43 and 4.98 per 100 person-years for urethral and anal chlamydia, respectively. Urethral infections were associated with unprotected anal intercourse (UAI) with HIV-positive partners (hazard ratio (HR) = 2.58, 95% CI 1.10 to 6.05 for urethral gonorrhoea) and with frequent insertive oral sex (p for trend 0.007 for urethral chlamydia). Anal infections were associated with receptive UAI (p for trend 0.001 for both anal gonorrhoea and chlamydia) and other receptive anal sexual practices. Stratified analyses showed the independence of the associations of insertive oral sex with urethral infections and of non-intercourse receptive anal practices with anal infections. CONCLUSION: Incident gonorrhoea and chlamydia were common. Risk behaviours for both urethral and anal infections were not restricted to UAI. Screening that includes tests for anal and urethral infections should be considered for all sexually active homosexual men, not just for those who report UAI.

Safe sex after post-exposure prophylaxis for HIV: intentions, challenges and ambivalences in narratives of gay men.

This paper draws on findings from an on-going prospective cohort study, with a quantitative and a qualitative arm, to monitor the implementation of non-occupational post-exposure prophylaxis (PEP) in Australia. The aim of the qualitative arm was to explore in-depth details of exposures to HIV and participants' understanding of 'risk'. Of the 328 patients who were enrolled in the study from March 1999 to July 2001, 88 (27%) participated in the qualitative arm. Interviews were conducted in a semi-structured style and explored the event that precipitated the request for PEP, participants' understanding of safe sex, their physical and psychological experience of the treatment and the impact that the availability of PEP may have on their sexual practices in the future. One theme running through the interviews was a determination to either maintain existing high levels of safe sex or to increase safe sex practices in those men who perceived PEP as 'a wake up call'. This determination was motivated by the experience of taking combination therapies and reflection on a potentially HIV-positive future. However, there were also tensions and ambivalences in the narratives. PEP was promoted as an adjunct to safe sex, not as an alternative. This is how PEP was understood by the men in this study.

Differences between men who report frequent, occasional or no unprotected anal intercourse with casual partners among a cohort of HIV-seronegative gay men in Sydney, Australia.

Past research on unprotected anal intercourse with casual partners (UAIC) contrasts those who report no UAIC with any UAIC. This paper examines differences among three groups of men who had any UAIC on the basis of the number of UAIC acts reported in a six-month period, namely no UAIC (n = 507), occasional UAIC (1-5 acts, n = 251) and frequent UAIC (more than 5 acts, n = 148). The occasional UAIC group had values lying between those of the no- and the frequent-UAIC group. As compared with the frequent-UAIC group, men in the occasional-UAIC group were less likely to have a steady partner, held less favorable attitudes toward condoms and higher levels of HIV treatments optimism and were more likely to report some disclosure of serostatus to or by casual partners and a range of esoteric sexual practice. On the other hand, men in the no-UAIC group had lower levels of 'feeling bad' (distress) and were less likely to use drugs to enhance sexual pleasure in casual encounters. Disclosure of serostatus had a strong association with frequent UAIC and this finding calls for both more research and more community exploration of issues surrounding sexual decision-making.

HIV risk and communication between regular partners in a cohort of HIV-negative gay men.

This paper reports on the breaking of agreements between regular partners among HIV-negative gay men in Sydney. Data were from the 1333 men completing face-to-face interviews through December 2003 for the Health in Men (HIM) open cohort of HIV-negative gay men in Sydney.822 men had a primary regular partner during the six month period before their 2003 interview. Most of these men had entered into agreements with their partners about sex either with each other or with other partners (87.2%). They most commonly agreed not to use condoms with each other (50.6%). Regarding casual sex, they most commonly agreed to always use condoms (34.2%) or to have no sex with men outside their relationships (28.6%). 48.8% reported some discomfort discussing with their partner their sex outside the relationship. Among those with agreements with their partners, 27.7% reported ever breaking those agreements. Those who found it more difficult to discuss issues of HIV serostatus and sexuality were more likely to report having broken their agreements (p<.001; p=.021 at one-year follow-up) and were more likely to have engaged in unprotected anal intercourse with casual partners (p<.001). A third of those men who broke their agreements did not inform their partner. A substantial proportion of gay men with agreements with their regular partners report some discomfort discussing sexuality and HIV serostatus with their partners. Difficulty discussing these issues may place these men at increased risk of breaking their agreements and may place both themselves and their partners at increased risk of infection.

Trends and predictors of HIV-positive community attachment among PLWHA.

Communities most affected by HIV/AIDS have been instrumental in shaping Australia's responses to the threat of the epidemic. There are recent signs that levels of engagement in communities based around HIV-positivity have changed: a diminished sense of an AIDS crisis, the relative success of highly active antiretroviral therapy (HAART), and an increasing individualization of the HIV experience may be contributing to changes in the way HIV-community is experienced. In this paper, we explore levels of engagement in HIV-positive community among a cohort of people living with HIV/AIDS (PLWHA) and seek to explain why some PLWHA engage in an HIV-positive community while others do not. Using multivariate logistic regression, we found that three factors were independently related to feeling part of an HIV-positive community: having been diagnosed with HIV prior to the advent of HAART; having more recently taken Bactrim or Septrin for PCP; and finding it easier to take 'pills' on time. Taken together, these results suggest that both historical effects, such as the introduction of HAART, and effects related to living with HIV, such as the experience of an AIDS-related illness, help explain HIV-positive community engagement among PLWHA.

Contexts for last occasions of unprotected anal intercourse among HIV-negative gay men in Sydney: the health in men cohort.

The objective of the paper was to compare encounters involving unprotected anal intercourse (UAI) and protected anal intercourse (PAI) among HIV-negative gay men in Sydney. Data were from those completing baseline face-to-face interviews to end June 2003 for the Health in Men open cohort of HIV-negative gay men in Sydney. The 1,148 participants ranged in age from 18 to 75 years (median = 36). Three hundred and fifty-two (30.7%) reported an occasion of UAI with a casual partner in the previous 6 months and 531 (46.3%) reported an occasion of UAI with a regular partner in that same time. The men's most recent sexual contact with a casual partner involving UAI was distinguished from those involving PAI by a greater likelihood for both partners to disclose HIV serostatus (p = 0.006) and by respondents being more inclined to restrict themselves to the insertive position or to practise withdrawal during occasions involving any UAI than when a condom was used (p = 0.003 and p = 0.001 respectively). Neither location nor recreational drug use differentiated men's most recent sexual contacts involving UAI from those involving PAI. The decision by HIV-negative gay men to use condoms during sexual encounters with either regular or casual partners is guided more by HIV serostatus and risk reduction strategies than by other factors.

Seroconversion in context.

This paper describes the accounts that homosexually active men give of their HIV seroconversion and interrogates these accounts for risk discourses. In particular, this paper asks whether the risk discourses of HIV researchers and educators are present in the men's narratives of their own seroconversion. Such discourses make reference to 'unsafe' sex--particularly the practice of unprotected anal intercourse, numbers of sexual partners or 'promiscuity', and the disinhibiting effect of drugs and alcohol. The data are drawn from an ongoing case-series study of seroconversion in which men who had seroconverted were asked to give an account of the occasion on which they believe they were infected. A number of themes were identified in the men's accounts. The men's descriptions of what they believe to be the seroconversion event indicate that their attributions, i.e., the reasons they give for their HIV infection, vary depending on the context. Within regular relationships, breakdown of negotiated safety, love and intimacy, and fatalism were among the explanations given. Seroconversion attributed to casual sexual encounters was more likely to be explained in terms of pleasure, lack of control, and with reference to particular sexual settings. The ways in which men understood their HIV infection were informed both by the risk discourse of HIV researchers and also by the discourses of love and pleasure, as well as that of control.

Predictors of recent HIV testing in homosexual men in Australia.

OBJECTIVES: To describe time trends and other predictors of recent HIV testing among homosexual men enrolled in behavioural surveillance studies in Australia. METHODS: Repeated cross-sectional studies during the period 1996-2001 in Australian capital cities. Men were recruited from a variety of community-based settings, including gay community outdoor events, sex on premises venues, and social venues. They underwent a brief self-administered questionnaire in which they reported their HIV status, HIV-testing history, sexual behaviour and demographic information. RESULTS: Questionnaires were returned for 22,161 HIV-negative or status-unknown participants. While 85.3% had ever tested for HIV, 57.6% had tested in the last 12 months. Recent testing was greater in those living in Sydney, in younger men, in gay-identified men, in gay community-attached men, in those who reported unprotected anal intercourse and a higher number of sexual partners, and in partners of HIV-positive men. Although recent testing declined from 1996 to 2001, this trend was no longer significant when adjusted for other testing predictors. CONCLUSIONS: In Australia, HIV testing among gay men decreased slightly from 1996 to 2001, but the trend was not significant when adjusted for other predictors. Testing levels were highest among those at highest risk of HIV infection, and lowest among non gay-identified and non gay-community attached homosexual men.

In a minority of gay men, sexual risk practice indicates strategic positioning for perceived risk reduction rather than unbridled sex.

The aim of this analysis was to examine gay men's sexual risk practice to determine patterns of risk management. Ten cross-sectional surveys of gay men were conducted six-monthly from February 1996 to August 2000 at Sydney gay community social, sex-on-premises and sexual health sites (average n = 827). Every February during this period, five identical surveys were conducted at the annual Gay and Lesbian Mardi Gras Fair Day (average n = 1178). Among the minority of men who had unprotected anal intercourse which involved ejaculation inside with a serodiscordant regular partner, there was a clear pattern of sexual positioning. Few regular couples were both receptive and insertive. Most HIV-positive men were receptive and most HIV-negative men were insertive. Among the minority of men who had unprotected anal intercourse which involved ejaculation inside with casual partners, there was also a pattern of sexual positioning. Whereas many casual couples were both receptive and insertive (especially those involving HIV-positive respondents), among the remainder HIV-positive men tended to be receptive and HIV-negative men tended to be insertive. These patterns of HIV-positive/receptive and HIV-negative/insertive suggest strategic risk reduction positionings rather than mere sexual preferences among a minority of gay men. If so, they point not to complacency but to an ever more complex domain of HIV prevention.

Increasing proportions of Australian gay and homosexually active men engage in unprotected anal intercourse with regular and with casual partners.

We examined trends in sexual practice among gay and homosexually active men in Australia. Self-complete questionnaires were distributed with mail-order sex video catalogues in 2000 and returned anonymously through a reply-paid facility. The data were compared with those from men who responded to promotional material sent out with the same catalogues and who participated in national telephone surveys of men who have sex with men conducted in 1992 and 1996. A key independent variable was gay community attached (GCA) versus non-GCA (NGCA) derived from two items about number of gay friends and amount of free time spent with gay men. Responses came from 1,832 men ranging in age from 16 to 80 (median = 39) years. HIV status was 73% negative, 5% positive, 22% untested; 1,181 men were GCA and 651 men were NGCA. Overall, from 1992 to 2000 there was a significant upward trend in the proportion of men reporting any unprotected anal intercourse (UAI) in the previous six months with regular partners: 21.5%, 24.7%, 46.4% of the total sample (p < 0.001). And similarly for UAI with casual partners: 12.4%, 16.2%, 25.5% (p < 0.001). The upward trends in UAI-regular and UAI-casual were similar and significant (p < 0.001) for both GCA and NGCA men. These nationwide Australian data provide evidence of continuing increases in unprotected anal intercourse with regular and with casual partners. Whereas the majority of men do not engage in any unprotected anal intercourse during a defined interval, ever increasing proportions of them do.

Modelling the effect of combination antiretroviral treatments on HIV incidence.

OBJECTIVE: To assess the competing effects on HIV incidence in homosexual men of the decreased infectiousness of men with HIV receiving effective combination antiretroviral treatments and homosexual men engaging in unprotected anal intercourse with increased numbers of partners (levels of unsafe sex). METHODS: A mathematical model of HIV transmission in homosexual men was developed, based on the HIV epidemic in Australia in 1996, when effective antiretroviral treatments first became widely available. Uncertainties in parameters were modelled using 1000 simulations. The effect of treatments on decreasing infectiousness was randomly sampled with a median 10-fold decrease in infectiousness (range 100-fold to no decrease). Levels of unsafe sex were randomly sampled with a median 50% increase in unsafe sex (range 100% to no increase). The percentage change in HIV incidence after one year was obtained by comparison with a null model in which there was no decrease in infectiousness as a result of treatment and no change in unsafe sex. RESULTS: Results of the models suggested that whereas increased levels of unsafe sex were linearly associated with increases in HIV incidence, decreases in infectiousness because of treatments were non-linearly associated with decreases in HIV incidence. An assessment of the competing effects suggested that decreases in infectiousness of two-, five-, and 10-fold would be counterbalanced by increases in unsafe sex of approximately 40, 60 and 70%, respectively. CONCLUSION: These models suggest that apparently large decreases in infectiousness as a result of treatment could be counterbalanced in terms of new HIV infections by much more modest increases in unsafe sex.