Incidence of HIV-1 infection in a rural region of Uganda

Feasibility of establishing an HIV vaccine preparedness cohort in a population of the Uganda Police Force: Lessons learnt from a prospective study

Background

Members of uniformed armed forces are considered to be at high risk for HIV infection and have been proposed as suitable candidates for participation in HIV intervention studies. We report on the feasibility of recruitment and follow up of individuals from the community of the Uganda Police Force (UPF) for an HIV vaccine preparedness study.

Methods

HIV-negative volunteers aged 18–49 years, were identified from UPF facilities situated in Kampala and Wakiso districts through community HIV counselling and testing. Potential volunteers were referred to the study clinic for screening, enrolment and quarterly visits for one year. HIV incidence, retention rates were estimated and expressed as cases per 100 person years of observation (PYO). Rate ratios were used to determine factors associated with retention using Poisson regression models.

Results

We screened 560 to enroll 500 volunteers between November 2015 and May 2016. One HIV seroconversion occurred among 431 PYO, for an incidence rate of 0.23/100 PYO (95% confidence interval [CI]: 0.03–1.64). Overall, retention rate was 87% at one year, and this was independently associated with residence duration (compared to <1 year, 1 to 5 years adjusted rate ratio (aRR) = 1.19, 95%CI: 1.00–1.44); and >5 years aRR = 1.34, 95%CI: 0.95–1.37); absence of genital discharge in the last 3 months (aRR = 1.97, 95% CI: 1.38–2.83, absence of genital ulcers (aRR = 1.90, 95%CI: 1.26–2.87, reporting of new sexual partner in the last month (aRR = 0.57, 95%CI: 0.45–0.71, being away from home for more than two nights (aRR = 1.27, 95%CI: 1.04–1.56, compared to those who had not travelled) and absence of knowledge on HIV prevention (aRR = 2.67, 95%CI: 1.62–4.39).

Conclusions

While our study demonstrates the feasibility of recruiting and retaining individuals from the UPF for HIV research, we did observe lower than anticipated HIV incidence, perhaps because individuals at lower risk of HIV infection may have been the first to come forward to participate or participants followed HIV risk reduction measures. Our findings suggest lessons for recruitment of populations at high risk of HIV infection.

HIV prevalence by ethnic group covaries with prevalence of herpes simplex virus-2 and high-risk sex in Uganda: An ecological study

Background

HIV prevalence varies from 1.7% to 14.8% between ethnic groups in Uganda. Understanding the factors responsible for this heterogeneity in HIV spread may guide prevention efforts.

Methods

We evaluated the relationship between HIV prevalence by ethnic group and a range of risk factors as well as the prevalence of herpes simplex virus-2 (HSV-2), syphilis and symptomatic STIs in the 2004/2005 Uganda HIV/AIDS Sero-Behavioural Survey—a two stage, nationally representative, population based survey of 15–59-year-olds. Spearman’s correlation was used to assess the relationship between HIV prevalence and each variable.

Results

There was a positive association between HIV prevalence and HSV-2, symptomatic STIs and high-risk sex (sex with a non-cohabiting, non-marital partner) for women. Non-significant positive associations were present between HIV and high-risk sex for men and lifetime number of partners for men and women.

Conclusion

Variation in sexual behavior may contribute to the variations in HIV, HSV-2 and other STI prevalence by ethnic group in Uganda. Further work is necessary to delineate which combinations of risk factors determine differential STI spread in Uganda.

Using nearly full-genome HIV sequence data improves phylogeny reconstruction in a simulated epidemic

HIV molecular epidemiology studies analyse viral pol gene sequences due to their availability, but whole genome sequencing allows to use other genes. We aimed to determine what gene(s) provide(s) the best approximation to the real phylogeny by analysing a simulated epidemic (created as part of the PANGEA_HIV project) with a known transmission tree. We sub-sampled a simulated dataset of 4662 sequences into different combinations of genes (gag-pol-env, gag-pol, gag, pol, env and partial pol) and sampling depths (100%, 60%, 20% and 5%), generating 100 replicates for each case. We built maximum-likelihood trees for each combination using RAxML (GTR + Γ), and compared their topologies to the corresponding true tree’s using CompareTree. The accuracy of the trees was significantly proportional to the length of the sequences used, with the gag-pol-env datasets showing the best performance and gag and partial pol sequences showing the worst. The lowest sampling depths (20% and 5%) greatly reduced the accuracy of tree reconstruction and showed high variability among replicates, especially when using the shortest gene datasets. In conclusion, using longer sequences derived from nearly whole genomes will improve the reliability of phylogenetic reconstruction. With low sample coverage, results can be highly variable, particularly when based on short sequences.

Phylogenetic Tools for Generalized HIV-1 Epidemics: Findings from the PANGEA-HIV Methods Comparison

Viral phylogenetic methods contribute to understanding how HIV spreads in populations, and thereby help guide the design of prevention interventions. So far, most analyses have been applied to well-sampled concentrated HIV-1 epidemics in wealthy countries. To direct the use of phylogenetic tools to where the impact of HIV-1 is greatest, the Phylogenetics And Networks for Generalized HIV Epidemics in Africa (PANGEA-HIV) consortium generates full-genome viral sequences from across sub-Saharan Africa. Analyzing these data presents new challenges, since epidemics are principally driven by heterosexual transmission and a smaller fraction of cases is sampled. Here, we show that viral phylogenetic tools can be adapted and used to estimate epidemiological quantities of central importance to HIV-1 prevention in sub-Saharan Africa. We used a community-wide methods comparison exercise on simulated data, where participants were blinded to the true dynamics they were inferring. Two distinct simulations captured generalized HIV-1 epidemics, before and after a large community-level intervention that reduced infection levels. Five research groups participated. Structured coalescent modeling approaches were most successful: phylogenetic estimates of HIV-1 incidence, incidence reductions, and the proportion of transmissions from individuals in their first 3 months of infection correlated with the true values (Pearson correlation > 90%), with small bias. However, on some simulations, true values were markedly outside reported confidence or credibility intervals. The blinded comparison revealed current limits and strengths in using HIV phylogenetics in challenging settings, provided benchmarks for future methods' development, and supports using the latest generation of phylogenetic tools to advance HIV surveillance and prevention.

Combined Intimate Partner Violence and HIV/AIDS Prevention in Rural Uganda: Design of the SHARE Intervention Strategy

Intimate partner violence (IPV) has a bidirectional relationship with HIV infection. Researchers from the Rakai Health Sciences Program (RHSP), an HIV research and services organization in rural Uganda, conducted a combination IPV and HIV prevention intervention called the Safe Homes and Respect for Everyone (SHARE) Project between 2005 and 2009. SHARE was associated with significant declines in physical and sexual IPV and overall HIV incidence, and its model could be adopted as a promising practice in other settings. In this article we describe how SHARE's IPV-prevention strategies were integrated into RHSP's existing HIV programming and provide recommendations for replication of the approach.

Effects of hormonal contraceptive use on HIV acquisition and transmission among HIV-discordant couples

BACKGROUND

The risk of HIV associated with hormonal contraceptives is controversial. We assessed hormonal contraceptive use and HIV incidence in HIV-discordant couples in Rakai, Uganda.

METHODS

HIV-discordant couples were retrospectively identified from a cohort between 1999 and 2009. Hormonal contraception included oral contraception, depomedroxyprogesterone acetate (DMPA), and implants (Norplant). Poisson regression estimated adjusted incidence rate ratios (adjIRRs) associated with hormonal contraceptive methods. A case-control subanalysis estimated odds ratios (ORs) of HIV associated with hormonal contraceptive, adjusted for viral load and age.

RESULTS

We identified 190 male HIV-positive/female HIV-negative (M+F-) and 159 male HIV- negative/female HIV-positive (M-F+) couples not using antiretroviral therapy or condoms. Female HIV incidence was 5.8/100 person-years (py) among nonhormonal contraceptive users, 12.0/100 py among oral contraceptive users [adjIRR 2.65, 95% confidence interval (CI) 0.82-8.60], 4.5 among Norplant users (adjIRR: 0.89, 95% CI 0.11-7.10), and 7.5/100 py among DMPA users (adjIRR 1.42, 95% CI 0.60-3.36). Male HIV incidence was 7.4/100 py during nonhormonal contraceptive use, 16.5/100 py during female oral contraceptive use (adjIRR 2.52, 95% CI 0.49-12.95), and 4.9/100 py with DMPA use (adjIRR 0.57, 95% CI 0.19-1.70). The number of female seroconverters was three among oral contraceptive users, one among Norplant users, and seven among DMPA users. Male seroconverters were two during female oral contraceptive use, none with Norplant use, and three with DMPA use. In a nested case-control analysis after adjustment for HIV viral load, the adjOR associated with oral contraceptive use was 1.59 (95% CI 0.32-97.85) for M+F- and 2.11 (95% CI 0.18-25.26) for M-F+ couples. For DMPA use, the adjOR was 1.44 (95% CI 0.46-4.51) for M+F- and 1.40 (95% CI 0.30-6.49) for M-F+ couples.

CONCLUSION

We did not observe significant risk of HIV acquisition or transmission with oral contraceptives or DMPA use in HIV discordant couples, but several point estimates were above 1.0 and statistical power was limited.

Assessment of changes in risk behaviors during 3 years of posttrial follow-up of male circumcision trial participants uncircumcised at trial closure in Rakai, Uganda

Risk compensation associated with male circumcision has been a concern for male circumcision scale-up programs. Using posttrial data collected during 2007-2011 on 2,137 male circumcision trial participants who were uncircumcised at trial closure in Rakai, Uganda, the authors evaluated their sexual behavioral changes during approximately 3 years' follow-up after trial closure. Eighty-one percent of the men self-selected for male circumcision during the period, and their sociodemographic and risk profiles were comparable to those of men remaining uncircumcised. Linear models for marginal probabilities of repeated outcomes estimate that 3.3% (P < 0.0001) of the male circumcision acceptors reduced their engagement in nonmarital relations, whereas there was no significant change among men remaining uncircumcised. Significant decreases in condom use occurred in both male circumcision acceptors (-9.2% with all partners and -7.0% with nonmarital partners) and nonacceptors (-12.4% and -13.5%, respectively), and these were predominantly among younger men. However, the magnitudes of decrease in condom use were not significantly different between the 2 groups. Additionally, significant decreases in sex-related alcohol consumption were observed in both groups (-7.8% in male circumcision acceptors and -6.1% in nonacceptors), mainly among older men. In summary, there was no evidence of risk compensation associated with male circumcision among this cohort of men during 3 years of posttrial follow-up.

Exploring the potential impact of a reduction in partnership concurrency on HIV incidence in rural Uganda: a modeling study

BACKGROUND

A number of African countries have planned campaigns against concurrency. It will not be possible to separate the effects of a reduction in concurrency from other behavior changes when evaluating these campaigns. This modeling study explores the potential impact of an intervention to reduce partnership concurrency on HIV incidence in contemporary rural Uganda, keeping incidence of sex acts and partnerships in the population constant.

METHODS

Data on demography, sexual behavior, and HIV prevalence from Uganda were used to parameterize an individual-based HIV transmission model. Three baseline model scenarios were simulated, representing the best estimate of concurrency prevalence in this population, and low and high plausible bounds. Interventions that reduced concurrency by 20% and 50% between 2010 and 2020 were simulated, and the impact on HIV incidence in 2020 was calculated.

RESULTS

Data showed 9.6% (7.9%-11.4%) of men and 0.2% (0.0%-0.4%) of women reported concurrency in 2008. Reducing concurrency had a nonlinear impact on HIV incidence. A 20% reduction in concurrency reduced HIV incidence by 4.1% (0.3%-5.7%) in men and 9.2% (2.1%-16.8%) in women; a 50% reduction in concurrency reduced HIV incidence by 6.0% (1.4%-10.8%) in men and 16.2% (6.3%-23.4%) in women.

CONCLUSIONS

Interventions against concurrency have the potential to reduce HIV incidence and may have a higher impact in women than in men. In rural Uganda, overall impact was modest, and this study does not provide strong support for the prioritization of concurrency as a target for behavior change interventions. However, it may be more useful in higher concurrency settings and for reducing HIV incidence in women.

Demographic predictors of HIV serostatus among HIV counseling and testing clients in rural Nigeria

Nnewi is a rural Nigerian town with a human immunodeficiency virus (HIV) counseling and testing center which tests about 120 clients/d. The objective of this study is to determine the factors predicting positive HIV status at Nnewi. Review of records was done with age, gender, marital status, and occupation as variables. Logistic regression analysis was used to identify factors linked to a positive HIV test. Overall HIV prevalence was 31.14%. Drivers and married clients had a high risk of being HIV+ (odds ratio [OR], 3.59; 95% confidence interval [CI], 2.17-5.96 and OR, 2.78; 95% CI, 2.42-3.19). Housewives were 2 times more likely to be positive (OR, 2.11; 95% CI, 1.35-3.29). After adjustment, females had 22% higher risk (OR, 1.22; 95% CI, 1.03-1.45) with the highest chance found in married females (OR, 6.70; 95% CI, 4.45-10.09). The study succeeded in panning out an unexpected risk group: married women. Drivers have been known to be a risk group. Preventive methods must be tailored to and acceptable by each risk group.

The rates of HIV superinfection and primary HIV incidence in a general population in Rakai, Uganda

BACKGROUND

Human immunodeficiency virus (HIV) superinfection has been documented in high-risk individuals; however, the rate of superinfection among HIV-infected individuals within a general population remains unknown.

METHODS

A novel next-generation ultra-deep sequencing technique was utilized to determine the rate of HIV superinfection in a heterosexual population by examining two regions of the viral genome in longitudinal samples from recent HIV seroconverters (n=149) in Rakai District, Uganda.

RESULTS

The rate of superinfection was 1.44 per 100 person years (PYs) (95% confidence interval [CI], .4-2.5) and consisted of both inter- and intrasubtype superinfections. This was compared to primary HIV incidence in 20 220 initially HIV-negative individuals in the general population in Rakai (1.15 per 100 PYs; 95% CI, 1.1-1.2; P= .26). Propensity score matching (PS) was used to control for differences in sociodemographic and behavioral characteristics between the HIV-positive individuals at risk for superinfection and the HIV-negative population at baseline and follow-up. After PS matching, the estimated rate of primary incidence was 3.28 per 100 PYs (95% CI, 2.0-5.3; P = .07) controlling for baseline differences and 2.51 per 100 PYs (95% CI, 1.5-4.3; P = .24) controlling for follow-up differences.

CONCLUSIONS

This suggests that the rate of HIV superinfection in a general population is substantial, which could have a significant impact on future public health and HIV vaccine strategies.

More on the cohort-component model of population projection in the context of HIV/AIDS: A Leslie matrix representation and new estimates

This article presents an extension of the cohort-component model of population projection (CCMPP) first formulated by Heuveline (2003) that is capable of modeling a population affected by HIV. Heuveline proposes a maximum likelihood approach to estimate the age profile of HIV incidence that produced the HIV epidemics in East Africa during the 1990s. We extend this work by developing the Leslie matrix representation of the CCMPP, which greatly facilitates the implementation of the model for parameter estimation and projection. The Leslie matrix also contains information about the stable tendencies of the corresponding population, such as the stable age distribution and time to stability. Another contribution of this work is that we update the sources of data used to estimate the parameters, and use these data to estimate a modified version of the CCMPP that includes (estimated) parameters governing the survival experience of the infected population. A further application of the model to a small population with high HIV prevalence in rural South Africa is presented as an additional demonstration. This work lays the foundation for development of more robust and flexible Bayesian estimation methods that will greatly enhance the utility of this and similar models.

Uncovering high rates of unsafe injection equipment reuse in rural Cameroon: validation of a survey instrument that probes for specific misconceptions

BACKGROUND

Unsafe reuse of injection equipment in hospitals is an on-going threat to patient safety in many parts of Africa. The extent of this problem is difficult to measure. Standard WHO injection safety assessment protocols used in the 2003 national injection safety assessment in Cameroon are problematic because health workers often behave differently under the observation of visitors. The main objective of this study is to assess the extent of unsafe injection equipment reuse and potential for blood-borne virus transmission in Cameroon. This can be done by probing for misconceptions about injection safety that explain reuse without sterilization. These misconceptions concern useless precautions against cross-contamination, i.e. "indirect reuse" of injection equipment. To investigate whether a shortage of supply explains unsafe reuse, we compared our survey data against records of purchases.

METHODS

All health workers at public hospitals in two health districts in the Northwest Province of Cameroon were interviewed about their own injection practices. Injection equipment supply purchase records documented for January to December 2009 were compared with self-reported rates of syringe reuse. The number of HIV, HBV and HCV infections that result from unsafe medical injections in these health districts is estimated from the frequency of unsafe reuse, the number of injections performed, the probability that reused injection equipment had just been used on an infected patient, the size of the susceptible population, and the transmission efficiency of each virus in an injection.

RESULTS

Injection equipment reuse occurs commonly in the Northwest Province of Cameroon, practiced by 44% of health workers at public hospitals. Self-reported rates of syringe reuse only partly explained by records on injection equipment supplied to these hospitals, showing a shortage of syringes where syringes are reused. Injection safety interventions could prevent an estimated 14-336 HIV infections, 248-661 HBV infections and 7-114 HCV infections each year in these health districts.

CONCLUSIONS

Injection safety assessments that probe for indirect reuse may be more effective than observational assessments. The autodisable syringe may be an appropriate solution to injection safety problems in some hospitals in Cameroon. Advocacy for injection safety interventions should be a public health priority.

HIV-1 incidence rates and risk factors in agricultural workers and dependents in rural Kenya: 36-month follow-up of the Kericho HIV cohort study

BACKGROUND

Incidence data from prospective cohort studies using rigorous laboratory methods are important in designing and evaluating HIV vaccine and therapeutic clinical trials and health care programs. We report 36-month HIV-1 incidence rates and demographic and psychosocial risks from the Kericho cohort in rural Kenya's southern Rift Valley Province.

METHODS

Thirty-six month, prospective, closed, observational cohort study of adult plantation workers and dependents followed biannually. HIV-1 incidence rates per 100 person-years (py) were calculated, and Cox regression analyses were used to estimate hazards ratios (HR) associated with seroconversion.

RESULTS

Two thousand four hundred volunteers (mean age +/- SD = 30.1 +/- 8.5 years; 36.5% women) participated. Twenty-nine new HIV cases were identified in year 1 of follow-up, which increased to cumulative totals of 49 and 63 cases in years 2 and 3, respectively. The corresponding 1-, 2-, and 3-year incidence rates were 1.41 [95% confidence interval (CI) = 0.95-2.02], 1.16 (95% CI = 0.86-1.54), and 1.00 (95% CI = 0.77-1.28) per 100 py. Risk factors associated with HIV seroconversion included the following: of the Luo tribe (HR = 3.31; 95% CI = 1.65-6.63), marriage more than once (HR = 2.83; 95% CI = 1.20-6.69), self-reported male circumcision (HR = 0.32; 95% CI = 0.17-0.60), history of sexually transmitted infection (HR = 2.40; 95% CI = 1.09-5.26), history of substance abuse during sex (HR = 2.44; 95% CI = 1.16-5.13), and history of transactional sex (HR = 3.30; 95% CI = 1.79-6.09).

CONCLUSIONS

HIV-1 incidence rates were relatively low in adult plantation workers and dependents in rural Kenya. Cohorts including higher risk populations (eg, commercial sex workers) warrant consideration for regional HIV preventive vaccine trials. Even low incidence, well-described cohorts generate valuable epidemiological clinical trial data.

Rethinking the role of the local community in HIV epidemic spread in sub-Saharan Africa: a proximate-determinants approach

The spread of HIV in sub-Saharan Africa continues largely unabated. To improve prevention interventions, a better understanding of the determinants of HIV infection is required. Conceptual frameworks can guide epidemiological investigation and prevent a misguided focus on single risk factors in isolation. Existing frameworks of HIV infection focus on transmission. However, the transmitting individual is rarely known. By contrast, data on individual HIV acquisition are available from longitudinal studies and tests for recent HIV infection. From the perspective of individuals susceptible to HIV, it is important to distinguish between factors determining the individual's biological disposition and sexual behavior and community-level factors, which can affect both HIV acquisition and the likelihood that a sex partner chosen from a community will be infected with HIV and transmit the infection. We propose a framework that takes the susceptible individual as a starting point and links distal, proximate and biological determinants of HIV infection at both the individual and the community level. We describe three necessary ingredients for the use of the framework (identification of the relevant community, multilevel analysis and methods for causal inference).

Microbial translocation, the innate cytokine response, and HIV-1 disease progression in Africa

Reports from the United States have demonstrated that elevated markers of microbial translocation from the gut may be found in chronic and advanced HIV-1 infection and are associated with an increase in immune activation. However, this phenomenon's role in HIV-1 disease in Africa is unknown. This study examined the longitudinal relationship between microbial translocation and circulating inflammatory cytokine responses in a cohort of people with varying rates of HIV-1 disease progression in Rakai, Uganda. Multiple markers for microbial translocation (lipopolysaccharide, endotoxin antibody, and sCD14) did not change significantly during HIV-1 disease progression. Moreover, circulating immunoreactive cytokine levels either decreased or remained virtually unchanged throughout disease progression. These data suggest that microbial translocation and its subsequent inflammatory immune response do not have a causal relationship with HIV-1 disease progression in Africa.

Reported number of sexual partners: comparison of data from four African longitudinal studies

OBJECTIVE

To compare reported numbers of sexual partners in Eastern and Southern Africa.

METHODS

Sexual partnership data from four longitudinal population-based surveys (1998-2007) in Zimbabwe, Uganda and South Africa were aggregated and overall proportions reporting more than one lifetime sexual partner calculated. A lexis-style table was used to illustrate the average lifetime sexual partners by site, sex, age group and birth cohort. The male-to-female ratio of mean number of partnerships in the last 12 months was calculated by site and survey. For each single year of age, the proportion sexually active in the past year, the mean number of partners in the past year and the proportion with more than one partner in the past year were calculated.

RESULTS

Over 90% of men and women between 25 and 45 years of age reported being sexually active during the past 12 months, with most reporting at least one sexual partner. Overall, men reported higher numbers of lifetime sexual partners and partners in the last year than women. The male-to-female ratio of mean partnerships in the last year ranged from 1.41 to 1.86. In southern African cohorts, individuals in later birth cohorts reported fewer sexual partners and a lower proportion reported multiple partnerships compared with earlier birth cohorts, whereas these behavioural changes were not observed in the Ugandan cohorts. Across the four sites, reports of sexual partnerships followed a similar pattern for each sex.

CONCLUSIONS

The longitudinal results show that reductions in the number of partnerships were more evident in southern Africa than in Uganda.

Localized spatial clustering of HIV infections in a widely disseminated rural South African epidemic

BACKGROUND

South Africa contains more than one in seven of the world's HIV-positive population. Knowledge of local variation in levels of HIV infection is important for prioritization of areas for intervention. We apply two spatial analytical techniques to investigate the micro-geographical patterns and clustering of HIV infections in a high prevalence, rural population in KwaZulu-Natal, South Africa.

METHODS

All 12,221 participants who consented to an HIV test in a population under continuous demographical surveillance were linked to their homesteads and geo-located in a geographical information system (accuracy of <2 m). We then used a two-dimensional Gaussian kernel of radius 3 km to produce robust estimates of HIV prevalence that vary across continuous geographical space. We also applied a Kulldorff spatial scan statistic (Bernoulli model) to formally identify clusters of infections (P < 0.05).

RESULTS

The results reveal considerable geographical variation in local HIV prevalence (range = 6-36%) within this relatively homogenous population and provide clear empirical evidence for the localized clustering of HIV infections. Three high-risk, overlapping spatial clusters [Relative Risk (RR) = 1.34-1.62] were identified by the Kulldorff statistic along the National Road (P < or = 0.01), whereas three low risk clusters (RR = 0.2-0.38) were identified elsewhere in the study area (P < or = 0.017).

CONCLUSIONS

The findings show the existence of several localized HIV epidemics of varying intensity that are partly contained within geographically defined communities. Despite the overall high prevalence of HIV in many rural South African settings, the results support the need for interventions that target socio-geographic spaces (communities) at greatest risk to supplement measures aimed at the general population.

HIV incidence in 3 years of follow-up of a Zimbabwe cohort--1998-2000 to 2001-03: contributions of proximate and underlying determinants to transmission

BACKGROUND

In recent years, HIV prevalence has begun to decline in Zimbabwe, which has been associated with reductions in sexual risk behaviour. Here, we analyse the determinants of HIV incidence in this period of decline and estimate the population-level impact of identified risk factors.

METHODS

A population-based cohort of 1672 HIV-negative adult males and 2465 HIV-negative adult females was recruited between 1998 and 2000. Each individual was then followed-up 3 years later. The influence and inter-relationship of social, behavioural and demographic variables were examined using a proximate determinants framework. To explore the population-level influence of a variable, methods were developed for estimating a risk factor's contribution to the reproductive number (CRN).

RESULTS

HIV incidence was 19.9 [95% confidence interval (CI) 16.3-24.2] per 1000 person years in men and 15.7 (95% CI 13.0-18.9) in women. Multiple sexual partners, having an unwell partner, and reporting another sexually transmitted disease were risk factors that captured the main aspects of the proximate determinants framework: individual behaviour, partnership characteristics and the probability of transmission, respectively. If the proximate determinants fully captured risk of HIV infection, underlying factors would not influence a fully parameterized model. However, a number of underlying social and demographic determinants remained important in regression models after including the proximate determinants. For both sexes, having multiple sexual partners made a substantial CRN, but, for women, no behaviour explained more than 10% of new infections.

CONCLUSIONS

The proximate determinants did not explain the majority of new infections at the population level. This may be because we have been unable to measure some risks, but identifying risk factors assumes that those acquiring infections are somehow different from others who do not acquire infections. That they are not suggests that in this generalized epidemic there is little difference in readily identifiable characteristics of the individual between those who acquire infection and those who do not.

A nested case-control study of sexual practices and risk factors for prevalent HIV-1 infection among young men in Kisumu, Kenya

OBJECTIVES

To investigate sexual practices and risk factors for prevalent HIV infection among young men in Kisumu, Kenya.

GOAL

The goal of this study was to identify behaviors associated with HIV in Kisumu to maximize the effectiveness of future prevention programs.

STUDY DESIGN

Lifetime sexual histories were collected from a nested sample of 1337 uncircumcised participants within the context of a randomized controlled trial of male circumcision to reduce HIV incidence.

RESULTS

Sixty-five men (5%) tested positive for HIV. Multiple logistic regression revealed the following independent predictors of HIV: older age, less education, being married, being Catholic, >4 lifetime sex partners, prior treatment for an STI, sex during partner's menstruation, ever practicing bloodletting, and receipt of a medical injection in the last 6 months. Prior HIV testing and postcoital cleansing were protective.

CONCLUSIONS

This analysis confirms the importance of established risk factors for HIV and identifies practices that warrant further investigation.

Trends in antenatal HIV prevalence in urban Uganda associated with uptake of preventive sexual behaviour

BACKGROUND

Epidemiological surveillance in Uganda has consistently shown declining HIV prevalence particularly among young antenatal women since the early 1990s, correlated with increased uptake of protective sexual behaviour.

OBJECTIVE

To describe trends in sexual behaviour nationwide and antenatal HIV prevalence from urban sentinel sites in Uganda (1989-2002).

METHODS

Review of antenatal HIV seroprevalence data from the sentinel surveillance system (1989-2002) and data on sexual behavioural indicators from the AIDS module of the National Demographic and Health Surveys (1989, 1995 and 2000/01). Trends in biological and behavioural indicators assessed.

RESULTS

Antenatal HIV seroprevalence in seven urban clinics peaked around 1992 (15-30%) followed by a steady decline by 2002 (5-12%), most markedly among women aged 15-19 and 20-24 years. This coincided with increased primary and secondary abstinence among young people nationwide. Median age at sexual debut increased from 16.5 in 1989 to 17.3 in 2000 for women and from 17.6 in 1995 to 18.3 in 2000 for men. Premarital sex among women and multiple partnerships decreased between 1995 and 2000. There were no significant changes in reporting of extramarital sex among men. Ever use of condoms increased from 1% among women in 1989 and 16% among men in 1995 to 16% and 40% in 2000, respectively. Between 1995 and 2000, condom use at last sex with a non-regular partner increased from 35% to 59% and 20% to 39% among men and women, respectively.

CONCLUSION

The ecological correlation between the trends in HIV prevalence and incidence and the increase in protective sexual behaviour during the 1990s makes a compelling case for continuing prevention efforts in Uganda.

Use of stored serum from Uganda for development and evaluation of a human immunodeficiency virus type 1 testing algorithm involving multiple rapid immunoassays

We report the development and evaluation of a human immunodeficiency virus type 1 testing algorithm consisting of three rapid antibody detection tests. Stored serum samples from Uganda were utilized with a final algorithm sensitivity of 100% and a specificity of 98.9% (95% confidence interval, 98.6% to 99.3%).

High-risk behaviour in young men attending sexually transmitted disease clinics in Pune, India

The present study reports sexual risk factors associated with HIV infection among men attending two sexually transmitted disease (STD) clinics in Pune, India and compares these behaviours between young and older men. Between April 1998 and May 2000, 1872 STD patients were screened for HIV infection. Data on demographics, medical history and sexual behaviour were collected at baseline. The overall HIV prevalence was 22.2%. HIV risk was associated with being divorced or widowed, less educated, living away from the family, having multiple sexual partners and initiation of sex at an early age. The risk behaviours in younger men were different to older men. Younger men were more likely to report early age of initiation of sex, having friends, acquaintances or commercial sex workers as their regular partners, having premarital sex and bisexual orientation. Young men were more educated and reported condom use more frequently compared with the older men. Similar high HIV prevalence among younger and older men highlights the need for focused targeted interventions aimed at adolescents and young men and also appropriate interventions for older men to reduce the risk of HIV and STD acquisition.

Methodological lessons from a cohort study of high risk women in Tanzania

OBJECTIVES

To describe the development, characteristics, and follow up of a high risk cohort of women in Tanzania. Differences in social background and sexual behaviour of women working in traditional and modern alcohol selling workplaces are shown.

METHODS

Data from questionnaires four months before the enrollment of the cohort, at enrollment, and at 32 months were compared. Key informant interviews, social mapping exercises, and focus group discussions were held before the start of the cohort.

RESULTS

In the absence of organised prostitution, two different groups of women with high risk exposure were identified during the baseline survey: female workers in modern alcohol selling places such as bars, guesthouses, and restaurants (barmaids) and in traditional places (local brew sellers). Overall, the population had a mean age of 27.7 years with barmaids tending to be younger (24.3 years) than local brew sellers (34.2 years). The main duration of stay in the current workplace was 2.1 years (barmaids 0.9 years; local brew sellers 4.1 years). Barmaids were more likely to have paying casual sex partners than local brew sellers and used condoms more regularly. Local brew sellers tend to be more stable with only 10% lost to follow up after 32 months compared with 24.4% of the bar workers.

CONCLUSIONS

Preliminary work revealed major differences in characteristics and behaviour between women working in modern and traditional alcohol selling outlets. Thorough preparation of the study, close monitoring of the cohort, and provision of selected benefits resulted in high retention rates over a 32 month project in a highly mobile population.

Transmission of HIV-1 infection in sub-Saharan Africa and effect of elimination of unsafe injections

During the past year, a group has argued that unsafe injections are a major if not the main mode of HIV-1 transmission in sub-Saharan Africa. We review the main arguments used to question the epidemiological interpretations on the lead role of unsafe sex in HIV-1 transmission, and conclude there is no compelling evidence that unsafe injections are a predominant mode of HIV-1 transmission in sub-Saharan Africa. Conversely, though there is a clear need to eliminate all unsafe injections, epidemiological evidence indicates that sexual transmission continues to be by far the major mode of spread of HIV-1 in the region. Increased efforts are needed to reduce sexual transmission of HIV-1.

The effects of alternative study designs on the power of community randomized trials: evidence from three studies of human immunodeficiency virus prevention in East Africa

BACKGROUND

Randomized intervention trials in which the community is the unit of randomization are increasingly being used to evaluate the impact of public health interventions. In the design of community randomized trials (CRT), the power of the study is likely to be affected by two issues: the matching or stratification of communities, and the number and size of the communities to be randomized.

METHODS

Data from three East African community intervention trials, designed to evaluate the impact of interventions to reduce human immunodeficiency virus (HIV) incidence, are used to compare the efficiency of different trial designs.

RESULTS

Compared with an unmatched design, stratification reduced the between-community variation in the Mwanza trial (from 0.51 to 0.24) and in the Masaka trial (from 0.38 to 0.28). The reduction was smaller in the Rakai trial where the selected communities were more homogeneous (from 0.15 to 0.11). For all trials, individual matching of communities produced estimates of between-community variation similar to those from the stratified designs. The linear association between HIV prevalence and incidence was strong in the Mwanza trial (correlation coefficient R = 0.83) and the Masaka trial (R = 0.83), but weak in the Rakai trial (R = 0.28). Unmatched study designs that use smaller communities tend to increase between-community variation, but reduce the design effect and improve study power.

CONCLUSIONS

These empirical data suggest that selection of homogeneous communities, or stratification of communities prior to randomization, may improve the power of CRT.

HIV and population dynamics: a general model and maximum-likelihood standards for east Africa

In high-prevalence populations, the HIV epidemic undermines the validity of past empirical models and related demographic techniques. A parsimonious model of HIV and population dynamics is presented here and fit to 46,000 observations, gathered from 11 East African populations. The fitted model simulates HIV and population dynamics with standard demographic inputs and only two additional parameters for the onset and scale of the epidemic. The underestimation of the general prevalence of HIV in samples of pregnant women and the fertility impact of HIV are examples of the dynamic interactions that demographic models must reproduce and are shown here to increase over time even with constant prevalence levels. As a result, the impact of HIV on population growth appears to have been underestimated by current population projections that ignore this dynamic.

Generalizability of population-based studies on AIDS: a comparison of newly and continuously surveyed villages in rural southwest Uganda

BACKGROUND

Population-based studies are thought to provide generalizable epidemiological data on the human immunodeficiency virus type 1 (HIV-1) epidemic. However, longitudinal studies are susceptible to bias from added attention caused by study activities. We compare HIV-1 prevalence in previously and newly surveyed villages in rural southwest Uganda.

METHODS

The study population resided in 25 neighbouring villages, of which 15 have been surveyed for 10 years. Respondents (>/=13 years) provided socio-demographic and sexual behaviour data and a blood sample for HIV-1 serology in private after informed consent. We tested the independent effect of residency: (1) original versus new villages; (2) proximity to main road; and (3) proximity to trading centre on HIV-1 serostatus of respondents using multivariate logistic regression.

RESULTS

There were 8,990 adults censused, 68.3% were from the original villages, 48.2% were males and 6111 (68.0%) were interviewed and had definite HIV-1 serostatus. The HIV-1 prevalence was 6.1% overall, 5.7% in the new, and 6.4% in the original villages (P = 0.25). Residency in the new or original villages did not independently predict HIV-1 serostatus of respondents (P = 0.46). Independent predictors of HIV-1 serostatus were education (primary or higher, odds ratio [OR] = 1.7 and 1.4, respectively), being separated or widowed OR = 4.2, reported previous use of a condom OR = 1.8, or reported genital ulceration OR = 3.3, and age group 25-34 and 35-44 years OR = 5.8 and OR = 4.8 (all P </= 0.001).

CONCLUSIONS

In the context of rural Uganda where there has been considerable health education about AIDS, the additional attention to HIV infection caused by this longitudinal study does not appear to have appreciably affected the prevalence of HIV-1 infection.

"It's not what you know, but who you knew": examining the relationship between behavior change and AIDS mortality in Africa

Until there is an effective vaccine, changing sexual behavior (e.g., use of condoms or fewer partners) is still the only course of action that can slow the spread of HIV for most Africans. But exactly which factors influence behavior change and how are still debated. This article examines the notion that as the HIV/AIDS epidemic strengthens and spreads through communities in Africa, and mortality mounts, behaviors that prevent transmission should be changing. We focus on men in three countries--Uganda, Kenya, and Zambia--examining determinants of their behavior change, and analyze the relative importance of knowing someone who has died of AIDS as compared with other factors such as age, education level, knowledge of HIV/AIDS, economic status, and marital status. Data from three DHS surveys in Uganda (1995), Zambia (1996), and Kenya (1998) are fitted to a model predicting behavior change. Results from this cross-sectional, multinational study suggest that married and working men aged 20-40 are significantly more likely to have changed their behavior. Personal experience of AIDS is a significant predictor of behavior change in Uganda and Zambia, and is marginally significant in Kenya. One implication in the context of the epidemic is that behavior change is partly determined by the high level of mortality experienced by African communities. A second implication is that higher levels of disclosure, or lower levels of denial of AIDS as a cause of death, may help individuals change their behavior.

Male circumcision and HIV acquisition and transmission: cohort studies in Rakai, Uganda. Rakai Project Team

BACKGROUND

Male circumcision is associated with reduced HIV acquisition.

METHODS

HIV acquisition was determined in a cohort of 5507 HIV-negative Ugandan men, and in 187 HIV-negative men in discordant relationships. Transmission was determined in 223 HIV-positive men with HIV-negative partners. HIV incidence per 100 person years (py) and adjusted rate ratios (RR) and 95% confidence intervals (CI) were estimated by Poisson regression. HIV-1 serum viral load was determined for the seropositive partners in HIV-discordant couples.

RESULTS

The prevalence of circumcision was 16.5% for all men; 99.1% in Muslims and 3.7% in non-Muslims. Circumcision was significantly associated with reduced HIV acquisition in the cohort as a whole (RR 0.53, CI 0.33-0.87), but not among non-Muslim men. Prepubertal circumcision significantly reduced HIV acquisition (RR 0.49, CI 0.26-0.82), but postpubertal circumcision did not. In discordant couples with HIV-negative men, no serconversions occurred in 50 circumcised men, whereas HIV acquisition was 16.7 per 100 py in uncircumcised men (P = 0.004). In couples with HIV-positive men, HIV transmission was significantly reduced in circumcised men with HIV viral loads less than 50000 copies/ml (P = 0.02).

INTERPRETATION

Prepubertal circumcision may reduce male HIV acquisition in a general population, but the protective effects are confounded by cultural and behavioral factors in Muslims. In discordant couples, circumcision reduces HIV acquisition and transmission. The assessment of circumcision for HIV prevention is complex and requires randomized trials.

Monitoring the AIDS epidemic using HIV prevalence data among young women attending antenatal clinics: prospects and problems

OBJECTIVE

To assess the potential of antenatal surveillance data on HIV prevalence in young women as an indicator of trends in HIV incidence.

DESIGN

Review of empirical data and discussion of problems encountered with surveillance systems, illustrated using cohort-component projection models.

METHODS

Simple descriptive analyses are presented of prevalence and incidence data, with projection models used to explore aspects of the dynamic relationships between changes in HIV incidence and prevalence in young pregnant women for which empirical data are not yet available. Incidence changes due to change in risk among sexually active, and change in pattern of sexual debut are explored separately, and the resulting prevalence trends in pregnant women under age 25 years, and those expecting their first two births are described.

RESULTS

HIV prevalence levels in young pregnant women categorized by age and by parity have different relationships to recent incidence levels. Age categorized prevalence data provide a reasonable indication of incidence under stable conditions, but may be very misleading if the age pattern of sexual debut changes. Prevalence levels categorized by parity are a reliable guide to incidence in the sexually active, but not necessarily to incidence in the population as a whole.

CONCLUSIONS

Ante-natal surveillance systems should categorize prevalence data by both age and parity to aid in the interpretation of underlying incidence levels.

Case-control study of risk factors for incident HIV infection in rural Uganda

OBJECTIVE

To identify risk factors associated with HIV incidence in a rural Ugandan population.

DESIGN

Case-control study.

METHODS

Men and women who seroconverted between 1990 and 1997 (cases) and seronegative subjects (controls) were drawn from a general population cohort of approximately 5000 adults in rural, southwestern Uganda. Information on risk factors was ascertained through a detailed interview and physical examination by clinicians who were blind to the study subjects' HIV status. All patients were interviewed within 2 years of their estimated date of seroconversion.

RESULTS

Data were available on 130 men (37 cases, 93 controls) and 133 women (46 cases, 87 controls). There was a significantly higher risk of infection in men (odds ratio [OR], 6.51; 95% confidence interval [CI], 1.06-39.84) and women (OR, 4.75; 95% CI, 1.26-17.9) who were unmarried and in a steady relationship, and in men who were divorced, separated, or widowed (OR, 4.33; 95% CI, 1.32-14.25) compared with those who were married. There was a significantly higher risk of HIV infection in men (OR, 3.78; 95% CI, 1.20-11.93) and women (OR, 20.78; 95% CI, 2.94-141.2) who reported > or =5 lifetime sexual partners compared with those who reported at most 1 partner. For men, there was an increased risk of infection associated with receiving increasing numbers of injections in the 6 months prior to interview (p < .001 for trend). Women reporting sex against their will in the year prior to interview were at higher risk of infection (OR, 7.84; 95% CI, 1.29-47.86; p = .020).

CONCLUSIONS

The strongest risk factor for HIV incidence in this rural Ugandan population is lifetime sexual partners. The increased risks found for women reporting coercive sex and men reporting injections require further investigation.

HIV incidence and HIV-associated mortality in a cohort of factory workers and their spouses in Tanzania, 1991 through 1996

OBJECTIVE

To describe HIV incidence and HIV-associated mortality in a cohort of factory workers and their spouses with access to adequate sexually transmitted diseases (STD) treatment services and moderate exposure to sexual health interventions.

METHODS

Follow-up visits at 4-month intervals and home follow-up of those who failed to keep appointments were used to estimate HIV incidence and mortality in a cohort of factory workers and their spouses in Mwanza, Tanzania, during 1991 to 1996.

RESULTS

HIV prevalence at intake was 10.5% and 15.3% among 1,594 men and 880 women, respectively. HIV incidence was just over 1/100 person-years (PY) in 1,427 men and 1.9/100 PY in 745 women. The main risk factors were related to sexual behavior and clinical evidence of an STD, although only one seventh of those with HIV seroconversions had had an STD during the period following the second-from-last follow-up visit. HIV incidence among discordant couples was 5.0 and 8.3/100 PY for 41 men and 37 women, respectively. Mortality rates were 9.0 and 7.8/1,000 PY for men and women, respectively, and 65% of male and 60% of female deaths were attributable to HIV infection.

CONCLUSIONS

In this factory population with good access to and use of STD treatment and with a moderate level of exposure to HIV prevention education, HIV incidence among men and women is still over 1/100 PY, which suggests a relatively high level of program effort is needed to lower incidence. More than half of all adult deaths were attributable to HIV, but greater increases in HIV-associated mortality are likely.

Age of male circumcision and risk of prevalent HIV infection in rural Uganda

OBJECTIVE

To assess whether circumcision performed on postpubertal men affords the same level of protection from HIV-1 acquisition as circumcisions earlier in childhood.

DESIGN

Cross-sectional study of a population-based cohort.

SETTING

Rakai district, rural Uganda.

METHODS

A total of 6821 men aged 15-59 years were surveyed and venous blood samples were tested for HIV-1 and syphilis. Age at circumcision was dichotomized into men who were circumcised before or at age 12 years (prepubertal) and men circumcised after age 12 years (postpubertal). Postpubertal circumcised men were also subdivided into those reporting circumcision at ages 13-20 years and > or = 21 years.

RESULTS

HIV-1 prevalence was 14.1% in uncircumcised men, compared with 16.2% for men circumcised at age > or = 21 years, 10.0% for men circumcised at age 13-20 years, and 6.9% in men circumcised at age < or = 12 years. On bivariate analysis, lower prevalence of HIV-1 associated with prepubertal circumcision was observed in all age, education, ethnic and religious groups. Multivariate adjusted odds ratio of prevalent HIV-1 infection associated with prepubertal circumcision was 0.39 [95% confidence interval (CI), 0.29-0.53]. In the postpubertal group, the adjusted odds ratio for men circumcised at ages 13-20 years was 0.46 (95% CI, 0.28-0.77), and 0.78 (95% CI, 0.43-1.43) for men circumcised after age 20 years.

CONCLUSIONS

Prepubertal circumcision is associated with reduced HIV risk, whereas circumcision after age 20 years is not significantly protective against HIV-1 infection. Age at circumcision and reasons for circumcision need to be considered in future studies of circumcision and HIV risk.

Control of sexually transmitted diseases for AIDS prevention in Uganda: a randomised community trial. Rakai Project Study Group

BACKGROUND

The study tested the hypothesis that community-level control of sexually transmitted disease (STD) would result in lower incidence of HIV-1 infection in comparison with control communities.

METHODS

This randomised, controlled, single-masked, community-based trial of intensive STD control, via home-based mass antibiotic treatment, took place in Rakai District, Uganda. Ten community clusters were randomly assigned to intervention or control groups. All consenting residents aged 15-59 years were enrolled; visited in the home every 10 months; interviewed; asked to provide biological samples for assessment of HIV-1 infection and STDs; and were provided with mass treatment (azithromycin, ciprofloxacin, metronidazole in the intervention group, vitamins/anthelmintic drug in the control). Intention-to-treat analyses used multivariate, paired, cluster-adjusted rate ratios.

FINDINGS

The baseline prevalence of HIV-1 infection was 15.9%. 6602 HIV-1-negative individuals were enrolled in the intervention group and 6124 in the control group. 75.0% of intervention-group and 72.6% of control-group participants provided at least one follow-up sample for HIV-1 testing. At enrolment, the two treatment groups were similar in STD prevalence rates. At 20-month follow-up, the prevalences of syphilis (352/6238 [5.6%]) vs 359/5284 [6.8%]; rate ratio 0.80 [95% CI 0.71-0.89]) and trichomoniasis (182/1968 [9.3%] vs 261/1815 [14.4%]; rate ratio 0.59 [0.38-0.91]) were significantly lower in the intervention group than in the control group. The incidence of HIV-1 infection was 1.5 per 100 person-years in both groups (rate ratio 0.97 [0.81-1.16]). In pregnant women, the follow-up prevalences of trichomoniasis, bacterial vaginosis, gonorrhoea, and chlamydia infection were significantly lower in the intervention group than in the control group. No effect of the intervention on incidence of HIV-1 infection was observed in pregnant women or in stratified analyses.

INTERPRETATION

We observed no effect of the STD intervention on the incidence of HIV-1 infection. In the Rakai population, a substantial proportion of HIV-1 acquisition appears to occur independently of treatable STD cofactors.

Sexual behaviour and risk assessment of HIV seroconvertors among urban male factory workers in Zimbabwe

Despite extensive HIV prevention programmes and knowledge of people dying of AIDS, people in Zimbabwe continue to be infected with HIV and other sexually transmitted infections (STIs). This paper presents selected case histories from interviews with 57 men who became HIV positive during follow up of 1678 seronegative male factory workers in Harare, and describes the circumstances in which they were exposed to infection. Youth was a major risk factor, with 47% of those who seroconverted aged between 18 and 24 yr. STIs were reported by 23% of the group in the seroconversion period, a marker of unprotected sex. Individuals did not recognise themselves or their partners as candidates for infection because of categorisation of high risk groups as "promiscuous" or clients of sex workers. Many were optimistic that they had changed sufficiently by using condoms more often or by avoiding sex workers. They made inaccurate assessments of who was safe for unprotected sex, based on judgements about their character, background and age. Over 40% of the seroconvertors had previously been counselled on staying HIV negative. Community approaches which nurture development of supportive group norms, respect for human rights and responsibilities, and safe environments for disclosure of HIV status, are vital for overcoming denial of risk at individual and societal levels. Special efforts targeted at youth are crucial since they have the highest risk of new infections and include use of media, drama, role models, advisory centres, peer education programmes. Health professionals need training and skills to enable people at risk of HIV infection to devise strategies based on more realistic personal risk assessment.

Estimating HIV incidence from age-specific prevalence data: comparison with concurrent cohort estimates in a study of male factory workers, Harare, Zimbabwe

OBJECTIVE

To compare HIV incidence estimates from cross-sectional age-specific prevalence data with concurrent cohort estimates and to examine the sensitivity of the estimates to changes in age-categorization and survivorship assumptions.

METHODS

Two previously described methods of estimating HIV incidence from cross-sectional prevalence data - the cumulative incidence and survival (CIS) and constant prevalence (CP) methods - are applied using data from a study of male factory workers in Harare, Zimbabwe. The methods are applied under two alternative groupings of the HIV prevalence data and under alternative survivorship assumptions: (a) Weibull distribution providing the best fit to the HIV prevalence data using the CIS method; (b) Weibull distribution matching data from an HIV natural history cohort study in Uganda; and (c) survivorship pattern as in (b) with survival periods reducing with increasing age at infection. Age-specific, age-standardized and cumulative HIV incidence estimates are calculated. The results are compared with concurrent longitudinal estimates from 3 years of follow-up of the Harare cohort (1993-1995).

RESULTS

Age-standardized HIV incidence was estimated at 2.02 per 100 man years (95% CI, 1.57-2.47) in the cohort study. There was evidence of recent variability in HIV incidence in these data. Estimates from the cross-sectional methods ranged from 1.98 to 2.74 per 100 man years and were sensitive to changes in age-categorization of the HIV prevalence data and changes in survivorship assumptions. The cross-sectional estimates were higher at central ages and lower at older ages than the cohort estimates. The age-specific estimates from the CIS method were less sensitive to changes in age grouping than those from the CP method.

CONCLUSIONS

HIV incidence remains high in Harare. Incidence estimates broadly consistent with cohort estimates can be obtained from single-round cross-sectional HIV prevalence data in established epidemics - even when the underlying assumption of stable endemic prevalence is not fully met. Estimates based on cross-sectional surveys should therefore be explored when reliable longitudinal estimates cannot be obtained. More data on post-HIV infection survivorship distributions in sub-Saharan Africa would facilitate the improvement of estimates of incidence based on cross-sectional surveys.

A randomized, community trial of intensive sexually transmitted disease control for AIDS prevention, Rakai, Uganda

OBJECTIVE

To describe the design and first-round survey results of a trial of intensive sexually transmitted disease (STD) control to reduce HIV-1 incidence.

STUDY DESIGN

Randomized, controlled, community-based trial in Rakai District, Uganda.

METHODS

In this ongoing study, 56 communities were grouped into 10 clusters designed to encompass social/sexual networks; clusters within blocks were randomly assigned to the intervention or control arm. Every 10 months, all consenting resident adults aged 15-59 years are visited in the home for interview and sample collection (serological sample, urine, and, in the case of women, self-administered vaginal swabs). Sera are tested for HIV-1, syphilis, gonorrhea, chlamydia, trichomonas and bacterial vaginosis. Following interview, all consenting adults are offered directly observed, single oral dose treatment (STD treatment in the intervention arm, anthelminthic and iron-folate in the control arm). Treatment is administered irrespective of symptoms or laboratory testing (mass treatment strategy). Both arms receive identical health education, condom and serological counseling services.

RESULTS

In the first home visit round, the study enrolled 5834 intervention and 5784 control arm subjects. Compliance with interview, sample collection and treatment was high in both arms (over 90%). Study arm populations were comparable with respect to sociodemographic and behavioral characteristics, and baseline HIV and STD rates. The latter were high: 16.9% of all subjects were HIV-positive, 10.0% had syphilis, and 23.8% of women had trichomonas and 50.9% had bacterial vaginosis.

CONCLUSIONS

Testing the effects of STD control on AIDS prevention is feasible in this Ugandan setting.

Is there evidence for behaviour change in response to AIDS in rural Zimbabwe?

This article reports on evidence for behaviour change in response to AIDS among women in two rural areas of Manicaland Province, Zimbabwe. It examines self-reported data on two overlapping areas of behaviour: (1) actions taken to avoid HIV-1 infection; and (2) fertility practices. The latter were used to assess the validity of the former, given that self-reported behaviour data are notoriously problematic. It is concluded that while self-reported behaviour change is exaggerated, the true level of change has nonetheless been significant and includes delayed onset of sexual relations, increased use of condoms and, possibly, increased monogamy. Reported actions taken to avoid HIV-1 infection and differentials in fertility practices were correlated with data on demographic, social and psychological factors. Differentials in fertility practices were associated with heightened risk perception--particularly when based on personal acquaintance with AIDS patients--but not with greater knowledge of HIV-1/AIDS. Results from the study suggest that effective behaviour change in Manicaland is facilitated by greater knowledge, experience and personal risk perception but obstructed by low female autonomy, marital status and economic status, and by male labour migration and alcohol consumption. Gaps in knowledge included misconceptions about the distinction between HIV-1 and AIDS, the influence of STDs, perinatal transmission, and incorrect modes of transmission. Better knowledge was associated with education, religion, travel and media exposure Personal risk perception was quite high (42%) and correlated with non-marriage, media exposure and contact with medical services. Few respondents knew close relatives with HIV/AIDS (4%) but nearly a quarter of those who felt in danger of infection said this was because friends and relatives were dying of AIDS. Many reported credible behavioural responses, some of which would only be effective given their partner's co-operation. Intensified behaviour interventions are needed which should include peer-education initiatives targeting men and individuals without access to modern media. The epidemic may accelerate fertility decline in rural Zimbabwe through behavioural as well as biological change.

Risk factors for Kaposi's sarcoma in HIV-positive subjects in Uganda

BACKGROUND

Kaposi's sarcoma (KS) is associated epidemiologically with HIV infection and with human herpesvirus 8 (HHV-8 or KSHV). Both KS and HIV infection are common in Uganda. We conducted a case-control study of 458 HIV-seropositive. Ugandan adults with KS and 568 HIV-seropositive subjects without KS to examine risk factors for HIV-associated KS.

METHODS

We recruited newly diagnosed adult KS cases from five hospitals in Kampala, Uganda and controls from a large referral clinic for HIV infection at Mulago Hospital. All cases and controls were counselled and tested for HIV and answered an interviewer-administered questionnaire about their home, socio-economic conditions, lifestyle and sexual behaviour before they became ill. Only HIV-seropositive subjects were included in the analysis.

RESULTS

There were 295 males and 163 females with KS and 227 male and 341 female controls. Age distribution was similar but there was a higher proportion of cases (45%) than controls (29%) residing in rural regions of Uganda. KS cases were more likely than controls to have a higher level of education (X2 for trend, 4.8; P = 0.03), to have occupations associated with affluence [chi 2 for heterogeneity, 17.3 on 5 degrees of freedom (df); P = 0.004] and to come from larger settlements [adjusted odds ratio (OR) for settlements of > 1000 versus 10-99 houses, 1.8; 95% confidence interval (CI), 1.1-3.0]. Cases were more likely than controls to have high household income (chi 2 for trend, 32.6; P < 0.001) and other markers of urban or rural wealth such as owning several cows (chi 2 for trend, 9.5; P = 0.002). Cases were more likely to travel away from home (adjusted OR, 1.6; 95% CI, 1.1-2.3) and more likely to have spent increasing time in contact with water (chi 2 for trend, 12.3; P < 0.001). Few indices of sexual behaviour were related to risk of KS, including reported number of sexual partners. Cases were more likely than controls to be married to one rather than several spouses (adjusted OR, 1.6; 95% CI, 1.2-2.2) and to have reported a history of sexually transmitted diseases (STD) (adjusted OR, 1.6; 95% CI, 1.2-2.3).

CONCLUSIONS

Among HIV-infected subjects, KS cases are characterized by better education and greater affluence, compared with controls. Urban address, travel away from home, exposure to water, monogamous marriage and self-reported STD were also more frequent among KS cases than controls. The higher socio-economic status of persons with HIV and KS may be a marker for enhanced exposure to a possibly sexually transmitted agent, or for a delayed exposure to a childhood infection. The risk posed by exposure to water among KS cases requires further study.

HIV-1 risk and vaccine acceptability in the Ugandan military

Between July and October 1993, 570 19- to 22-year-old volunteers were screened for HIV-1, with a resulting seroprevalence rate of 18.3% (95% CI: 14.0%, 22.6%). A cohort of 249 HIV-1-noninfected military recruits in the Ugandan Peoples' Defense Forces was followed prospectively for up to 18 months to document rates of HIV-1 seroprevalence, seroconversion, and knowledge and attitudes related to vaccine acceptability. The HIV-1 seroincidence rate was 3.56 per 100 person-years (95% CI: 1.49, 5.62) over 309 person-years of observation. At the 3- and 12-month visits, subjects were interviewed on issues of acceptance and knowledge about vaccines, including anti-HIV vaccines in particular. More than 90% believe that HIV vaccines will not cause HIV infection, and if offered, 88% report that they would take the vaccine if they were not already infected. Nonvaccine prevention methods were considered less reliable; monogamy and condom use were considered effective by only 33.5% and 69.3% of the cohort respectively. After completing the vaccine acceptability questionnaire at the 12-month visit, subjects were offered an approved polyvalent meningococcal vaccine as an indicator of general vaccine acceptance. All subjects reported receiving at least one previous vaccination, and 95% willingly accepted the meningococcal vaccination. The Ugandan military is a stable population at substantial risk for HIV-1 infection and may be a suitable population for vaccine efficacy trials.

Trends in HIV-1 prevalence may not reflect trends in incidence in mature epidemics: data from the Rakai population-based cohort, Uganda

OBJECTIVES

To assess whether trends in serial HIV-1 prevalence reflect trend in HIV incidence, and to decompose the effects of HIV-1 incidence, mortality, mobility and compliance on HIV-1 prevalence in a population-based cohort.

DESIGN

Two-year follow up (1990-1992) of an open cohort of all adults aged 15-59 years, resident in a sample of 31 representative community clusters in rural Rakai District, Uganda.

METHODS

A detailed household enumeration was concluded at baseline and in each subsequent year. All household residents were listed, and all deaths and in- and out-migrations that occurred in the intersurvey year wee recorded. In each year, all consenting adults were interviewed and provided a serological sample; 2591 adults aged 15-59 years were enrolled at baseline.

RESULTS

HIV prevalence among adults declined significantly 1990 and 1992 (23.4% at baseline, 21.8% in 1991, 20.9% in 1992; P < 0.05). Declining prevalence was also observed in subgroups, including young adults aged 15-24 years (from 20.6 to 16.2% over 3 years; P < 0.02), women of reproductive age (from 27.1 to 23.5%; P < 0.05), and pregnant women (from 25.4 to 20.0%; not significant), However, HIV incidence did not change significantly among all adults aged 15-59 years (2.1 +/- 0.4 per 100 person-years of observation (PYO) in 1990-1991 and 2.0 +/- 0.3 per 100 PYO in 1991-1992], nor in population subgroups. HIV-related mortality was high (13.5 per 100 PYO among the HIV-positive), removing more infected persons that were added by seroconversion. Net out-migration also removed substantial numbers of HIV-positive individuals.

CONCLUSIONS

In this mature HIV epidemic, HIV prevalence declined in the presence of stable and incidence. HIV-related mortality contributed most to the prevalence decline. Prevalence was not an adequate surrogate measure of incidence, limiting the utility or serial prevalence measures in assessing the dynamics of the HIV epidemic and in evaluating the impact of current preventive strategies.

Human immunodeficiency virus type 2 (HIV-2) seroprevalence and characterization of a distinct HIV-2 genetic subtype from the natural range of simian immunodeficiency virus-infected sooty mangabeys

The extent of zoonotic infections in rural Sierra Leone, where both feral and pet sooty mangabeys harbor divergent members of the human immunodeficiency virus type 2 (HIV-2)-sooty mangabey simian immunodeficiency virus (SIVsm) family, was tested in blood samples collected from 9,309 human subjects in 1993. Using HIV-1- and HIV-2-specific enzyme immunoassays and confirmatory Western blot analysis to test for antibodies to SIVsm-related lentiviruses, we found only nine subjects (0.096%) who tested positive for HIV: seven tested positive for HIV-1 and two tested positive for HIV-2. Compared with other rural West African communities, Sierra Leone displayed the lowest seroprevalence (0.021%) of HIV-2 infection yet reported, much lower than the previously reported seroprevalence in SIVsm-infected feral and household pet sooty mangabeys. Heteroduplex analysis demonstrated that two of the newly found HIV-1 strains belonged to subtype A, the most common HIV-1 subtype in Africa, but this is the first report of subtype A in Sierra Leone. The two HIV-2-infected individuals harbored two distinct HIV-2 strains, designated 93SL1 and 93SL2. Phylogenetic analysis indicated that HIV-2 93SL1 is a member of HIV-2 subtype A, the first strain of this HIV-2 subtype found in Sierra Leone. In contrast, HIV-2 93SL2 belongs to none of the five previously characterized HIV-2 subtypes (A to E) but is a new subtype, herein designated F, having the most divergent transmembrane sequences yet reported for HIV-2. The fact that both of the two most divergent HIV-2 subtypes known, E and F, are rare and found as single occurrences in persons from Sierra Leone may be related to the fact that this small region of West Africa also contains free-living and household pet sooty mangabeys with highly divergent variants of SIVsm. This finding provides support for the hypotheses that new HIV-2 subtypes result from independent cross-species transmission of SIVsm to the human population and that these single-occurrence transmission events had not spread widely into the population by 1993.

Adolescents, sexual behaviour and HIV-1 in rural Rakai district, Uganda

OBJECTIVES

To describe the epidemiology of HIV-1 infection among adolescents aged 13-19 years, in rural Rakai district, Uganda.

STUDY DESIGN

Baseline survey and 2-year follow-up (1990-1992) of adolescents in a population-based, open rural cohort.

METHODS

Annual enumeration and behavioral/serological survey of all consenting adolescents aged 13-19 years at recruitment, residing in 31 randomly selected community clusters.

RESULTS

At baseline, of 909 adolescents present in study clusters, 824 (90.6%) provided interview data and serological samples. No adolescents aged 13-14 years were HIV-infected. Among those aged 15-19 years, 1.8% of men and 19.0% of women were HIV-positive. Among young women aged 15-19 years in marital/consensual union, 21.3% were HIV-positive; this rate did not differ significantly from the 29.1% prevalence in those reporting non-permanent relationships; prevalence was significantly lower in women reporting no current relationship (4.3%). After multivariate adjustment, female sex, age 17-19 years, residence in trading centers/trading villages and a history of sexually transmitted disease symptoms remained significantly associated with HIV infection. Seventy-nine per cent of adolescents provided a follow-up serological sample. No young men aged 13-14 years seroconverted during the study; in young women aged 13-14 years, HIV seroincidence was 0.6 per 100 person-years (PY) of observation. Among young men aged 15-19 years, there were 1.1 +/- 0.6 seroconversions per 100 PY of observation prior to age 21 years; among women 15-19 years, the incidence rate was 3.9 +/- 1.0 per 100 PY of observation prior to age 21 years. The mortality rate among HIV-positive adolescents aged 15-19 years, at 3.9 per 100 PY of observation, was 13-fold higher than that among the HIV-uninfected. By 1992, knowledge of sexual transmission was almost universal, the proportions reporting multiple partners had decreased and condom use had increased over baseline.

CONCLUSIONS

Adolescents, and young women in particular, are vulnerable to HIV infection. Despite reported behavioral changes, HIV incidence rates remain substantial, and there is a need for innovative HIV preventive measures.