HIV Transmission In Population Research Articles

The Effectiveness of the UNAIDS Strategy«90-90-90»in Populations with Different Population Growth

Introduction. Available data indicate that the effectiveness of the strategy of "90-90-90" varies considerably between countries. For example, Australia with figures 90-90-79 (2016) has not achieved the negative trend of the incidence and prevalence, while Niger 35-90-57 performance demonstrates a stable decrease in the HIV epidemic. One possible explanation for the observed processes may have different development of the epidemic process in populations that differ by demographic characteristics. From this we can assume that the epidemic control in a strategy of «90-90-90» or any other strategies will differ significantly in such self-regulating systems. Aim: modeling the dynamics of the epidemic process in populations with different probability of HIV transmission and negative, zero, positive population growth. Materials and methods : Computer probabilistic modeling by the Monte Carlo method was carried out. The following parameters were used to describe the epidemic process: population size, birth rate, mortality, HIV prevalence, lethality among patients with HIV/AIDS and probability of HIV transmission. The values of these parameters were close to the UNAIDS global statistics. It is assumed that the effective management of the epidemic reduce the probability of HIV transmission in the population. The dynamics of the population size, incidence and prevalence of HIV infection in populations with negative, zero, positive natural growth and the probability of HIV transmission in the population from 50% to 10% has been consistently studied. Statistical processing carried out by the Student method. Results and discussion. In populations with a negative population growth and a probability of HIV transmission of 0.5, incidence and prevalence at the initial stage are characterized by an increasing trend, reach peak values and decrease to zero. When reducing the probability of HIV transmission peak becomes plateau or directly take the downward shape. In general terms, similar patterns are recorded at zero population growth. The incidence and prevalence of HIV infection with a positive population growth are changing cyclically up and down. Change transmission probabilities range from 0.5 to 0.2 is characterized by a decrease in the frequency and amplitude of peaks increasing incidence and prevalence. When transmission probabilities at 0.1 epidemic process drops sharply. According to the simulation, any managerial impact in countries with negative population growth should be effective. Practical evidence does not contradict theory. For example, indicators "56-66-59" in Ukraine led to a decrease in the incidence. Management actions in populations with positive population growth that reduce the probability of HIV transmission by 20% or 40% are ineffective. When reaching 80%, the epidemic process abruptly stops. Conclusions. The effect of reducing the probability of HIV transmission in populations with a negative and zero population growth is expressed as a linear reduction in incidence and prevalence (at fixed lethality). In populations with a positive natural growth reduction transmission probabilities less than 40% strategically not effective, and when it reaches 80% potentiated abrupt cessation epidemic process.

The Implications of Respondent Concurrency on Sex Partner Risk in a National, Web-Based Study of Men Who Have Sex With Men in the United States

Men who have sex with men (MSM) represent the largest HIV risk group in the United States. Sexual concurrency catalyzes HIV transmission in populations by increasing the indirect exposure of one's sex partners to one another. Although individual-level (egocentric) designs have demonstrated a high prevalence of concurrency among MSM respondents, methods are lacking for understanding the exposure implications for partners (dyads) reported in such studies. A new technique for manipulating egocentrically collected partnership timing data to measure the degree to which respondents' patterns of concurrency and serial monogamy resulted in the indirect exposure of respondents' partners to other partners was developed. Two outcomes were constructed for each partner: any concurrent or serially monogamous exposure to another partner (any exposure) and any concurrent exposure to another partner, irrespective of serial monogamy (any concurrent exposure). Reports of unprotected anal intercourse (UAI) were incorporated to construct the outcomes of 'any UAI exposure' and 'any concurrent UAI exposure.' This method was applied to an online study of MSM aged ≥18 years, with comparisons made by partner's race-ethnicity, age, type, and meeting location. Among 4060 repeat partners of 2449 MSM, 73% had any exposure in the previous 6 months; 58% had any concurrent exposure. Among UAI partners, 37% had concurrent UAI exposure. Black UAI partners were more likely than whites to have any concurrent UAI exposure [unadjusted odds ratio (95% confidence interval) = 1.34 (1.05 to 1.70)], as were casual UAI partners relative to main partners [unadjusted odds ratio (95% confidence interval) = 4.37 (3.58 to 5.35)]. In adjusted models, black UAI partners were significantly more likely to have any UAI exposure, but not concurrent UAI exposure. Casual UAI partners remained more exposed by both outcomes. Sex partners of MSM, particularly casual and black non-Hispanic partners, face a high degree of exposure to other partners.

Epidemiological research in the HIV field

In 1988, AIDS published the first issue of ‘a year in review’. Nearly 25 years later, the epidemiology section makes very interesting ‘re-reading’ [1]. By the end of the 1980s, we had a fairly good understanding of the mechanisms underlying the spread of HIV. As Michael Adler and Peter Piot pointed out, progress in epidemiological research was slowing down and we entered a period of ‘fine tuning of our knowledge’. They identified a number of gaps in our understanding. These included mechanisms of transmission, the natural history of HIV infection in adults and in children, the discrepancy of the HIV epidemics in the heterosexual populations in Europe and North America and Africa, the efficiency and risk factors of mother-to-child transmission of HIV, and the ‘incapacity and/or unwillingness’ of societies to deal rationally with drug use in the face of fulminant HIV epidemics among injecting drug users. Although this latter challenge still is topical in 2012, it is now difficult to imagine that there was a time when it was thought that ‘control of perinatal transmission will only be achieved through effective programs aimed at decreasing the spread of infection to women’. Yet, there was some hope already for a treatment that would prevent progression to AIDS, although it was going to be expensive and pose major challenges for health services. We undoubtedly have made a lot of progress since 1988. We have come to realize that ‘high-risk sexual behavior’ is much more complex than just ‘high numbers of lifetime sex partners’. Much more attention is now being paid to contextual factors that shape sexual behavior. We have a better understanding of factors that influence the efficiency of transmission of HIV. Numerous randomized trials have been conducted to test the effectiveness of interventions that have been developed based on findings from observational epidemiological and behavioral research. The most spectacular trials in terms of results were the ones testing the protective effect of male circumcision and the trials of the use of antiretroviral compounds in preventing mother-to-child transmission and sexual transmission. Trials of behavioral interventions have, by and large, given disappointing results. This has led to discussions about the suitability of community randomized controlled trials for evaluating the effectiveness of nonbiomedical prevention interventions [2]. The good news, however, is that in many parts of sub-Saharan Africa, HIV prevalence has been decreasing, apparently due to changes in behavior. The challenge is to try and understand what exactly happened in these populations and whether these favorable trends can be replicated elsewhere. Classical epidemiological methods will not allow us to come to grips with the complexities of epidemic trends and mathematical modeling has become an indispensable tool to try and understand the many factors that shape HIV epidemics. What are the major challenges for epidemiological research in 2012? We urgently need a reliable, easy-to-use tool to measure incidence at a population level. We still do not fully understand why the spread of HIV has been (and still is) so different in sub-Saharan Africa compared with heterosexual populations in other parts of the world and why the incidence of HIV infection in young women in southern Africa is so high. We need to revise what we know about the efficiency of HIV transmission in populations in different parts of the world. We also do not fully understand why in some gay communities HIV incidence has declined, whereas in other communities there is no decreasing trend despite high coverage with testing and antiretroviral treatment. And last but not least, how can we evaluate complex behavioral interventions in a reliable way? There is a consensus that there is no magic bullet (yet) to control HIV epidemics, and that we have to rely on combination prevention, including interventions at the structural and the individual level. Evaluating the effectiveness of combination prevention will have to rely on combination evaluation approaches using different data sources and mixed methods to build a plausible case. This will require interdisciplinary collaborations involving epidemiologists, mathematical modelers, and social scientists, and close collaboration between researchers and program implementers. Acknowledgements Conflicts of interest There are no conflicts of interest.

HIV Preexposure Prophylaxis in the United States: Impact on Lifetime Infection Risk, Clinical Outcomes, and Cost‐Effectiveness

The combination of tenofovir and emtricitabine shows promise as HIV preexposure prophylaxis (PrEP). We sought to forecast clinical, epidemiologic, and economic outcomes of PrEP, taking into account uncertainties regarding efficacy, the risks of developing drug resistance and toxicity, behavioral disinhibition, and drug costs. We adapted a computer simulation of HIV acquisition, detection, and care to model PrEP among men who have sex with men and are at high risk of HIV infection (i.e., 1.6% mean annual incidence of HIV infection) in the United States. Base-case assumptions included 50% PrEP efficacy and monthly tenofovir-emtricitabine costs of $753. We used sensitivity analyses to examine the stability of results and to identify critical input parameters. In a cohort with a mean age of 34 years, PrEP reduced lifetime HIV infection risk from 44% to 25% and increased mean life expectancy from 39.9 to 40.7 years (21.7 to 22.2 discounted quality-adjusted life-years). Discounted mean lifetime treatment costs increased from $81,100 to $232,700 per person, indicating an incremental cost-effectiveness ratio of $298,000 per quality-adjusted life-year gained. Markedly larger reductions in lifetime infection risk (from 44% to 6%) were observed with the assumption of greater (90%) PrEP efficacy. More-favorable incremental cost-effectiveness ratios were obtained by targeting younger populations with a higher incidence of infection and by improvements in the efficacy and cost of PrEP. PrEP could substantially reduce the incidence of HIV transmission in populations at high risk of HIV infection in the United States. Although it is unlikely to confer sufficient benefits to justify the current costs of tenofovir-emtricitabine, price reductions and/or increases in efficacy could make PrEP a cost-effective option in younger populations or populations at higher risk of infection. Given recent disappointments in HIV infection prevention and vaccine development, additional study of PrEP-based HIV prevention is warranted.