Short term estimates of adult HIV incidence by mode of transmission: Kenya and Thailand as examples

Millennium development goal 6 and HIV infection in Zambia: what can we learn from successive household surveys?

BACKGROUND

Geographic location represents an ecological measure of HIV status and is a strong predictor of HIV prevalence. Given the complex nature of location effects, there is limited understanding of their impact on policies to reduce HIV prevalence.

METHODS

Participants were 3949 and 10 874 respondents from two consecutive Zambia Demographic and Health Surveys from 2001/2007 (mean age for men and women: 30.3 and 27.7 years, HIV prevalence 14.3% in 2001/2002; 30.3 and 28.0 years, HIV prevalence of 14.7% in 2007). A Bayesian geo-additive mixed model based on Markov Chain Monte Carlo techniques was used to map the change in the spatial distribution of HIV/AIDS prevalence at the provincial level during the 6-year period, accounting for important risk factors.

RESULTS

Overall HIV/AIDS prevalence changed little over the 6-year period, but the mapping of residual spatial effects at the provincial level suggested different regional patterns. A pronounced change in odds ratios in Lusaka and Copperbelt provinces in 2001/2002 and in Lusaka and Central provinces in 2007 was observed following adjustment for spatial autocorrelation. Western province went from a lower prevalence area in 2001 (13.4%) to a higher prevalence area in 2007 (17.3%). Southern province went from the highest prevalence area in 2001 (17.3%) to a lower prevalence area in 2007 (15.9%).

CONCLUSION

Findings from two consecutive surveys corroborate the Zambian government's effort to achieve Millennium Developing Goal (MDG) 6. The novel finding of increased prevalence in Western province warrants further investigation. Spatially adjusted provincial-level HIV/AIDS prevalence maps are a useful tool for informing policies to achieve MDG 6 in Zambia.

Selecting HIV infection prevention interventions in the mature HIV epidemic in Malawi using the mode of transmission model

BACKGROUND

Malawi is reassessing its HIV prevention strategy in the light of a limited reduction in the epidemic. No community based incidence studies have been carried out in Malawi, so estimates of where new infections are occurring require the use of mathematical models and knowledge of the size and sexual behaviour of different groups. The results can help to choose where HIV prevention interventions are most needed.

METHODS

The UNAIDS Mode of Transmission model was populated with Malawi data and estimates of incident cases calculated for each exposure group. Scenarios of single and multiple interventions of varying success were used to identify those interventions most likely to reduce incident cases.

RESULTS

The groups accounting for most new infections were the low-risk heterosexual group - the discordant couples (37%) and those who had casual sex and their partners (a further 16% and 27% respectively) of new cases.Circumcision, condoms with casual sex and bar girls and improved STI treatment had limited effect in reducing incident cases, while condom use with discordant couples, abstinence and a zero-grazing campaign had major effects. The combination of a successful strategy to eliminate multiple concurrent partners and a successful strategy to eliminate all infections between discordant couples would reduce incident cases by 99%.

CONCLUSIONS

A revitalised HIV prevention strategy will need to include interventions which tackle the two modes of transmission now found to be so important in Malawi - concurrency and discordancy.

HIV and risk environment for injecting drug users: the past, present, and future

We systematically reviewed reports about determinants of HIV infection in injecting drug users from 2000 to 2009, classifying findings by type of environmental influence. We then modelled changes in risk environments in regions with severe HIV epidemics associated with injecting drug use. Of 94 studies identified, 25 intentionally examined risk environments. Modelling of HIV epidemics showed substantial heterogeneity in the number of HIV infections that are attributed to injecting drug use and unprotected sex. We estimate that, during 2010-15, HIV prevalence could be reduced by 41% in Odessa (Ukraine), 43% in Karachi (Pakistan), and 30% in Nairobi (Kenya) through a 60% reduction of the unmet need of programmes for opioid substitution, needle exchange, and antiretroviral therapy. Mitigation of patient transition to injecting drugs from non-injecting forms could avert a 98% increase in HIV infections in Karachi; whereas elimination of laws prohibiting opioid substitution with concomitant scale-up could prevent 14% of HIV infections in Nairobi. Optimisation of effectiveness and coverage of interventions is crucial for regions with rapidly growing epidemics. Delineation of environmental risk factors provides a crucial insight into HIV prevention. Evidence-informed, rights-based, combination interventions protecting IDUs' access to HIV prevention and treatment could substantially curtail HIV epidemics.

PPARgamma and LXR signaling inhibit dendritic cell-mediated HIV-1 capture and trans-infection

Dendritic cells (DCs) contribute to human immunodeficiency virus type 1 (HIV-1) transmission and dissemination by capturing and transporting infectious virus from the mucosa to draining lymph nodes, and transferring these virus particles to CD4+ T cells with high efficiency. Toll-like receptor (TLR)-induced maturation of DCs enhances their ability to mediate trans-infection of T cells and their ability to migrate from the site of infection. Because TLR-induced maturation can be inhibited by nuclear receptor (NR) signaling, we hypothesized that ligand-activated NRs could repress DC-mediated HIV-1 transmission and dissemination. Here, we show that ligands for peroxisome proliferator-activated receptor gamma (PPARgamma) and liver X receptor (LXR) prevented proinflammatory cytokine production by DCs and inhibited DC migration in response to the chemokine CCL21 by preventing the TLR-induced upregulation of CCR7. Importantly, PPARgamma and LXR signaling inhibited both immature and mature DC-mediated trans-infection by preventing the capture of HIV-1 by DCs independent of the viral envelope glycoprotein. PPARgamma and LXR signaling induced cholesterol efflux from DCs and led to a decrease in DC-associated cholesterol, which has previously been shown to be required for DC capture of HIV-1. Finally, both cholesterol repletion and the targeted knockdown of the cholesterol transport protein ATP-binding cassette A1 (ABCA1) restored the ability of NR ligand treated cells to capture HIV-1 and transfer it to T cells. Our results suggest that PPARgamma and LXR signaling up-regulate ABCA1-mediated cholesterol efflux from DCs and that this accounts for the decreased ability of DCs to capture HIV-1. The ability of NR ligands to repress DC mediated trans-infection, inflammation, and DC migration underscores their potential therapeutic value in inhibiting HIV-1 mucosal transmission.

HIV, hepatitis B, and hepatitis C prevalence and associated risk behaviors among female sex workers in three Afghan cities

OBJECTIVE

To assess prevalence of HIV, syphilis, and hepatitis B (HBV) and C virus (HCV) and associated risk behaviors among female sex workers (FSWs) in three Afghan cities.

DESIGN

Cross-sectional prevalence assessment.

METHODS

Consented FSWs from Jalalabad, Kabul, and Mazar-i-Sharif completed an interviewer-administered questionnaire, pretest and posttest counseling, and rapid and confirmatory testing for HIV, HCV, HBV, and syphilis. Logistic regression was used to detect correlates associated with HBV infection.

RESULTS

Of 520 participants, median age and age of initiating sex work were 29 and 23 years, respectively, and the median number of monthly clients was 12. Few FSWs reported ever having used illicit drugs (6.9%) or alcohol (4.7%). Demographic and risk behaviors varied significantly by enrollment site, with Kabul FSWs more likely to report sexually transmitted infection symptoms, longer sex work duration, and sex work in other cities. Prevalence of HIV was 0.19%, HCV was 1.92%, and HBV was 6.54%, with no cases of syphilis detected. HBV was independently associated with at least 12 clients monthly [adjusted odds ratio (AOR) = 3.15, 95% confidence interval (CI) 1.38-7.17], ever using alcohol (AOR = 2.61, 95%CI 1.45-4.69), anal sex (AOR = 2.42, 95%CI 1.15-5.08), and having children (AOR = 2.12, 95%CI 1.72-2.63) in site-controlled multivariable analysis.

CONCLUSION

Although prevalence of HIV, HCV, and syphilis is currently low in these three Afghan cities, risky sexual practices were common and associated with HBV. Programming inclusive of voluntary testing for HIV, viral hepatitis, and sexually transmitted infections, hepatitis vaccination, substance abuse prevention, and condom promotion for both FSWs and clients should be pursued in Afghanistan.

Loss of correlation between HIV viral load and CD4+ T-cell counts in HIV/HTLV-1 co-infection in treatment naive Mozambican patients

Seven hundred and four HIV-1/2-positive, antiretroviral therapy (ART) naïve patients were screened for HTLV-1 infection. Antibodies to HTLV-1 were found in 32/704 (4.5%) of the patients. Each co-infected individual was matched with two HIV mono-infected patients according to World Health Organization clinical stage, age +/-5 years and gender. Key clinical and laboratory characteristics were compared between the two groups. Mono-infected and co-infected patients displayed similar clinical characteristics. However, co-infected patients had higher absolute CD4+ T-cell counts (P = 0.001), higher percentage CD4+ T-cell counts (P < 0.001) and higher CD4/CD8 ratios (P < 0.001). Although HIV plasma RNA viral loads were inversely correlated with CD4+ T-cell-counts in mono-infected patients (P < 0.0001), a correlation was not found in co-infected individuals (P = 0.11). Patients with untreated HIV and HTLV-1 co-infection show a dissociation between immunological and HIV virological markers. Current recommendations for initiating ART and chemoprophylaxis against opportunistic infections in resource-poor settings rely on more readily available CD4+ T-cell counts without viral load parameters. These guidelines are not appropriate for co-infected individuals in whom high CD4+ T-cell counts persist despite high HIV viral load states. Thus, for co-infected patients, even in resource-poor settings, HIV viral loads are likely to contribute information crucial for the appropriate timing of ART introduction.

Estimating HIV Incidence in Populations Using Tests for Recent Infection: Issues, Challenges and the Way Forward

INTRODUCTION: HIV incidence is the rate of new infections in a population over time. HIV incidence is a critical indicator needed to assess the status and trends of the HIV epidemic in populations and guide and assess the impact of prevention interventions. METHODS: Several methods exist for estimating population-level HIV incidence: direct observation of HIV incidence through longitudinal follow-up of persons at risk for new HIV infection, indirect measurement of HIV incidence using data on HIV prevalence and mortality in a population, and direct measurement of HIV incidence through use of tests for recent infection (TRIs) that can differentiate "recent" from "non-recent" infections based on biomarkers in cross-sectional specimens. Given the limitations in measuring directly observed incidence and the assumptions needed for indirect measurements of incidence, there is an increasing demand for TRIs for HIV incidence surveillance and program monitoring and evaluation purposes. RESULTS: Over ten years since the introduction of the first TRI, a number of low-, middle-, and high-income countries have integrated this method into their HIV surveillance systems to monitor HIV incidence in the population. However, the accuracy of these assays for measuring HIV incidence has been unsatisfactory to date, mainly due to misclassification of chronic infections as recent infection on the assay. To improve the accuracy of TRIs for measuring incidence, countries are recommended to apply case-based adjustments, formula-based adjustments using local correction factors, or laboratory-based adjustment to minimize error related to assay misclassification. Multiple tests may be used in a recent infection testing algorithm (RITA) to obtain more accurate HIV incidence estimates. CONCLUSION: There continues to be a high demand for improved TRIs and RITAs to monitor HIV incidence, determine prevention priorities, and assess impact of interventions. Current TRIs have noted limitations, but with appropriate adjustments, interpreted in parallel with other epidemiologic data, may still provide useful information on new infections in a population. New TRIs and RITAs with improved accuracy and performance are needed and development of these tools should be supported.

HIV risk behaviors among three classes of female sex workers in Vietnam

Increases in the rate of HIV infection in Vietnam among female sex workers and their clients require more effective preventive interventions based on a better understanding of this population and important subgroups within it. Because little was known about women in the hospitality sex industry, this study compared demographic and work characteristics, history of sexually transmitted infections (STIs), and condom use among a sample of 310 female sex workers in low-, middle-, and high-class hospitality businesses in Ho Chi Minh City (mean age = 26.77 years, SD = 6.17). Data were collected through individual, face-to-face, semistructured interviews. Logistic regression models were used to identify demographic predictors of the incidence of STIs and reported condom use. Low occupational status was most strongly associated with a history of STIs, and use of condoms with new and regular clients also differed by occupational class. Implications are discussed.

Preventive HIV vaccine acceptability and behavioral risk compensation among high-risk men who have sex with men and transgenders in Thailand

Thailand, with the highest number of volunteers to have participated in preventive HIV-1 vaccine trials globally, may be an early adopter of HIV vaccines. We conducted a mixed methods investigation, including 30 in-depth interviews and a venue-based survey. We used a structured questionnaire including conjoint analysis and a fractional factorial experimental design to assess preventive HIV vaccine acceptability and risk compensation among 255 high-risk men who have sex with men (MSM) and transgenders (mean age=26.6 years). HIV vaccine acceptability ranged from 31.6 to 73.8 on a 100-point scale; mean=58.3 (SD=17.1). Vaccine-induced seropositivity (VISP) had the greatest impact on acceptability, followed by efficacy, side effects, duration of protection, out-of-pocket cost and social saturation. Over one-third (34.6%) reported intentions to increase post-vaccination risk behaviors in response to a highly efficacious HIV vaccine. Social and structural interventions to promote HIV vaccine uptake as a prosocial behavior, provide accessible assays to detect VISP, and subsidize vaccine costs, and support for uptake of partially efficacious vaccines in the context of combination prevention, will facilitate HIV vaccine dissemination in Thailand.

Men who have sex with men and HIV/AIDS in sub-Saharan Africa

Globally, men who have sex with men (MSM) continue to bear a high burden of HIV infection. In sub-Saharan Africa, same-sex behaviours have been largely neglected by HIV research up to now. The results from recent studies, however, indicate the widespread existence of MSM groups across Africa, and high rates of HIV infection, HIV risk behaviour, and evidence of behavioural links between MSM and heterosexual networks have been reported. Yet most African MSM have no safe access to relevant HIV/AIDS information and services, and many African states have not begun to recognise or address the needs of these men in the context of national HIV/AIDS prevention and control programmes. The HIV/AIDS community now has considerable challenges in clarifying and addressing the needs of MSM in sub-Saharan Africa; homosexuality is illegal in most countries, and political and social hostility are endemic. An effective response to HIV/AIDS requires improved strategic information about all risk groups, including MSM. The belated response to MSM with HIV infection needs rapid and sustained national and international commitment to the development of appropriate interventions and action to reduce structural and social barriers to make these accessible.

HIV transmission networks

PURPOSE OF REVIEW

Over the past several years, one segment of the complex field of HIV transmission dynamics - heterosexual networks - has dominated theoretical and empirical investigation. This review provides an overview of recent work on HIV risks and networks, with a focus on recent findings in heterosexual network dynamics.

RECENT FINDINGS

Qualitative (ethnographic) assessments have demonstrated the heterogeneity and complexity of heterosexual connections, particularly in Africa, where tradition, official polygamy, and unofficial multiperson arrangements have lead to concurrency of sexual partnerships. A large, quantitative study on Likoma Island, Malawi, demonstrated the considerable, interlocking sexual connections that arise from a high-concurrency sexual setting, even with a low average number of partnerships (low degree) of long duration. Such settings, as suggested by ethnographic studies, may be common in Africa and, coupled with newer information about transmissibility during acute and early infection, may provide a plausible explanation for endemic transmission and possibly for rapid HIV propagation.

SUMMARY

Recognition of high-concurrency, low-degree networks is an important development for understanding HIV transmission dynamics. Their relevance to heterosexual transmission, and possible extension to other epidemiologic settings, reinforces the heterogeneity and complexity of HIV transmission dynamics.

Advances and future directions in HIV surveillance in low- and middle-income countries

PURPOSE OF REVIEW

To present recent advances in HIV/AIDS surveillance methods in low- and middle-income countries.

RECENT FINDINGS

From 2001 to 2008, 30 low- and middle-income countries implemented national population-based surveys with HIV testing. Antenatal clinic HIV sentinel surveillance sites in sub-Saharan Africa increased from just over 1000 in 2003-2004 to almost 2500 in 2005-2006, becoming more representative of rural areas. Between 2003 and 2007, at least 122 behavioral surveys in low- and middle-income countries used respondent-driven sampling for surveillance among high-risk populations, although many countries with concentrated epidemics continue to have major sentinel surveillance gaps. Improvements have been made in modeling estimates of number of persons HIV infected, and systems are now in place to measure HIV drug resistance. However, the reliable monitoring of trends and the measuring of HIV incidence, morbidity, and mortality is still a challenge.

SUMMARY

In the past 5 years, there have been substantial improvements in the quantity and quality of HIV surveillance studies, especially in the countries with high prevalence. Further efforts should be made in countries that lack fully implemented surveillance systems to improve HIV incidence, morbidity, and mortality surveillance and to use data more effectively.

Subjective expectations in the context of HIV/AIDS in Malawi

In this paper we present a newly developed interactive elicitation methodology for collecting probabilistic expectations in a developing country context with low levels of literacy and numeracy, and we evaluate the feasibility and success of this method for a wide range of outcomes in rural Malawi. We find that respondents' answers about their subjective expectations take into account basic properties of probabilities, and vary meaningfully with observable characteristics and past experience. From a substantive point of view, the elicited expectations indicate that individuals are generally aware of differential risks. For example, individuals with lower incomes and less land rightly feel at greater risk of financial distress than people with higher socioeconomic status (SES), and people who are divorced or widowed rightly feel at greater risk of being infected with HIV than currently married individuals. Meanwhile many expectations-including the probability of being currently infected with HIV-are well-calibrated compared to actual probabilities, but mortality expectations are substantially overestimated compared to life table estimates. This overestimation may lead individuals to underestimate the benefits of adopting HIV risk-reduction strategies. The skewed distribution of expectations about condom use also suggests that a small group of innovators are the forerunners in the adoption of condoms within marriage for HIV prevention.

Factors associated with self-reported unprotected anal sex among male sex workers in Mombasa, Kenya

OBJECTIVES

: To identify social and behavioral characteristics associated with sexual risk behaviors among male sex workers who sell sex to men in Mombasa, Kenya.

METHODS

: Using time-location sampling, 425 men who had recently sold, and were currently willing to sell sex to men were invited to participate in a cross-sectional survey. A structured questionnaire was administered using handheld computers. Factors associated with self-reported unprotected anal sex with male clients in the past 30 days were identified and subjected to multivariate analysis.

RESULTS

: Thirty-five percent of respondents did not know HIV can be transmitted via anal sex, which was a significant predictor of unprotected anal sex [adjusted odds ratio (AOR) 1.92; 95% confidence interval (95% CI), 1.16-3.16]. Other associated factors included drinking alcohol 3 or more days per week (AOR, 1.63; 95% CI, 1.05-2.54), self-report of burning urination within the past 12 months (AOR, 2.07; 95% CI, 1.14-3.76), and having never been counseled or tested for HIV (AOR, 1.66; 95% CI, 1.07-2.57). Only 21.2% of respondents correctly knew that a water-based lubricant should be used with latex condoms.

CONCLUSIONS

: Male sex workers who sell sex to men in Mombasa are in acute need of targeted prevention information on anal HIV and STI transmission, consistent condom use, and correct lubrication use with latex condoms. HIV programs in Africa need to consider and develop specific prevention strategies to reach this vulnerable population.

Global epidemiology of HIV-AIDS

Although intravenous drug use is the major route of transmission in several countries, sexual transmission is the dominant mode of HIV spread globally, with a concomitant epidemic in infants borne to HIV-infected mothers. The HIV epidemic varies substantially from one geographic area to another, and three broad epidemic categories describe the diversity of features observed globally: low epidemic settings, centrzated epidemics, and generalized epidemics. The introduction of highly active antiretroviral therapy in industrialized countries has transformed AIDS from an inevitably fatal condition to a chronic, treatable condition, but this goal has yet to be realized in most resource-constrained settings that bear a disproportionate burden of infection. This article describes the modes of HIV transmission, geographic distribution of the evolving AIDS pandemic, and case studies of each of the three types of HIV epidemics, and presents global trends in AIDS and mortality.

Modeling HIV transmission risk among Mozambicans prior to their initiating highly active antiretroviral therapy

Understanding sexual behavior and assessing transmission risk among people living with HIV-1 is crucial for effective HIV-1 prevention. We describe sexual behavior among HIV-positive persons initiating highly active antiretroviral therapy (HAART) in Beira, Mozambique. We present a Bernoulli process model (tool available online) to estimate the number of sexual partners who would acquire HIV-1 as a consequence of sexual contact with study participants within the prior three months. Baseline data were collected on 350 HAART-naive individuals 18-70 years of age from October 2004 to February 2005. In the three months prior to initiating HAART, 45% (n = 157) of participants had sexual relationships with 191 partners. Unprotected sex occurred in 70% of partnerships, with evidence suggesting unprotected sex was less likely with partners believed to be HIV-negative. Only 26% of the participants disclosed their serostatus to partners with a negative or unknown serostatus. Women were less likely to report concurrent relationships than were men (21 versus 66%; OR 0.13; 95%CI: 0.06, 0.26). Given baseline behaviors, the model estimated 23.2 infections/1,000 HIV-positive persons per year. The model demonstrated HAART along with syphilis and herpes simplex virus type 2 (HSV-2) treatment combined could reduce HIV-1 transmission by 87%; increasing condom use could reduce HIV-1 transmission by 67%.

Improving analysis of the size and dynamics of AIDS epidemics

Supplement editors Peter D Ghys and Neff Walker and the Chair of the UNAIDS Reference Group on Estimates, Modelling and Projections, Geoff P Garnett, introduce 13 papers describing the data, methods, and tools used to produce the 2005 UNAIDS/WHO HIV and AIDS estimates