Sexual partnership patterns in malawi: implications for HIV/STI transmission

Knowledge and Attitude Related to Sexually Transmitted Infections and Contraceptive Use Among Patients Attending the Venereology Outpatient Department in Thiruvallur: A Cross-Sectional Study

Introduction Sexually transmitted infections (STIs), which contribute to a significant amount of mortality and morbidity in the reproductive life of adults, are infections that can be prevented by healthy sexual behavior and education about the same. This study aims to assess the knowledge and attitude toward STIs and contraceptive use among patients attending the Venereology Outpatient Department (OPD). Methods A hospital-based cross-sectional study was conducted among patients more than 18 years of age attending the Venereology OPD, Government Medical College and Hospital, Thiruvallur, India, from March to May 2024. The sample size was calculated to be 458. Data were collected using a self-administered, semi-structured questionnaire divided into four sections: sociodemographic characteristics, sexual risk behavior and their awareness of contraceptive use, knowledge of STI symptoms and transmission, and attitude of the patients toward STIs. Ethical approval (IEC/4/2022 dated 08.02.2024) and participant consent were obtained. Statistical analysis, including the chi-square test, was performed and results were presented. Results  Of the study population, 50.4% were males, 49.1% were females, and 0.4% (n=2) were transgender individuals. STI screening and treatment rates were 22.1% and 19.4%, respectively. Contraceptive use was highest among bisexual individuals (50%), followed by homosexual (15%) and heterosexual individuals (11.8%). Similarly, treatment for STIs was reported in 55% of homosexuals, 50% of bisexuals, and 15.8% of heterosexuals. Among participants with multiple sexual partners, 30% reported contraceptive use as compared to less than 10% of those with single partners. Treatment for STIs was also higher in participants with multiple partners (65.2%) as compared to those with single partners (11.5%). The median knowledge score about STIs was 6.32, with only 44.3% of participants demonstrating good knowledge. The median attitude score was 52.63, with 44.3% showing a positive attitude toward STIs. Conclusion  The overall knowledge and attitude towards STIs were below par. Thus, the current study has found the need for sexual health education among patients and to create awareness of contraceptive use to fill gaps in existing knowledge, which can further reduce the risk of STIs among them.

Prevalence of syphilis among people living with HIV who attend a large urban antiretroviral therapy clinic in Panama: a cross-sectional epidemiological study

Background

Syphilis is a serious global public health challenge. Despite prior progress in syphilis control, incidence has been increasing in recent years. Syphilis is a common coinfection among people living with HIV (PLHIV). In Panama, few data describe syphilis prevalence among PLHIV. We describe syphilis antibody and high-titer (⩾1:8) active syphilis prevalence and associated factors among individuals who attended an antiretroviral clinic.

Methods

A cross-sectional study was undertaken during February-March 2022 and September-October 2022 for adults (⩾18 year) assigned male and female at birth, respectively. Participants provided peripheral blood samples and self-administered a questionnaire. Samples were screened using immunochromatography; antibody-positive samples were tested using rapid plasma regain to 1:512 dilutions. Logistic regression was used to identify factors associated with syphilis antibody and high-titer active syphilis.

Results

In all, 378 participants gave blood samples; 377 individuals participated in the questionnaire (216 self-reported male sex [males], 158 female [females], and three intersex individuals). Median age was 36 years (interquartile range: 28-45 years). Overall, syphilis antibody prevalence was 32.3% (122/378) (males, 50.7% [108/2013]; females, 5.7% [9/158]; intersex individuals, 100.0% (3/3)], p < 0.01. High-titer active syphilis was found among 24.6% (n = 30) of samples with positive antibody test (males 27.8% [n = 30], females 0.0% [0/9], intersex individuals 0.0% [0/3]). Antibody positivity was associated in the multivariable model with males (50.7%, AOR = 24.6, 95%CI: 1.57-384.53). High-titer active syphilis was associated with younger participant age (18-30 years, 13.2%, OR = 4.82, 95%CI: 1.17-19.83); 31-40 years, 7.8%, OR = 4.24, 95%CI: 1.04-17.21 versus 3.2% >40 years), homosexual identity (16.0% OR = 34.2, 95%CI: 4.50-259.27 versus 0.6% among heterosexual identity); in the multivariable model, associated with sexual identity (bisexual 19.1%, AOR = 10.89, 95%CI: 1.00-119.06) compared to heterosexual identity (0.6%) and weakly associated with concurrency (⩾1 ongoing sexual relationships, 15.9%, AOR = 3.09, 95%CI: 0.94-10.14).

Conclusion

This study found very high prevalence of syphilis antibodies and high-titer syphilis among PLHIV in Panama. Those most affected are males, younger in age, those who practice concurrent sexual relationships, and those who reported homosexual and bisexual identity. Targeted interventions should include repetitive testing and treatment, especially among individuals who may be at increased infection risk.

Knowledge and attitude on sexually transmitted infections and contraceptive use among university students in Bhutan

Objectives

The unmet needs of contraception can lead to unintended pregnancy and transmission of sexually transmitted infections (STI). Therefore, this study aimed to evaluate the contraception use, knowledge, and attitude on STI among students under Royan University of Bhutan (RUB).

Methods

This was a cross-sectional study using an online questionnaire. The questionnaire was developed in Google forms and the link was shared through the college WeChat groups. The questionnaire consisted of four parts on socio-demographic, sexual behaviour and contraceptive use, knowledge, and attitude on STIs. All the students under RUB were invited to participate voluntarily in this study. The socio-demography was presented in frequency and proportion.

Result

A total of 1,283 students participated in this survey and 55.0% (701) were females. Of this, 29.4% (377) were sexually active and 94.4% reported using modern contraception. Commonly used contraceptives were: condoms (83.8%, 316) and emergency contraceptives (20.6%, 78), respectively. The mean knowledge and attitude scores on STI were 9.94 (range 2–20) and 12 (range 2–14), respectively. Good knowledge and attitude on STI were reported in 53.2% (683) and 70.1% (899) of participants.

Conclusion

Students reported average knowledge and a good attitude towards STI. Contraceptive use among university students was low. There is a need to strengthen health education on STIs in schools and universities. All forms of contraceptives especially condoms should be made easily available to sexually active people.

Large benefits to youth-focused HIV treatment-as-prevention efforts in generalized heterosexual populations: An agent-based simulation model

Predominantly heterosexual HIV-1 epidemics like those in sub-Saharan Africa continue to have high HIV incidence in young people. We used a stochastic, agent-based model for age-disparate networks to test the hypothesis that focusing uptake and retention of ART among youth could enhance the efficiency of treatment as prevention (TasP) campaigns. We used the model to identify strategies that reduce incidence to negligible levels (i.e., < 0.1 cases/100 person-years) 20-25 years after initiation of a targeted TasP campaign. The model was parameterized using behavioral, demographic, and clinical data from published papers and national reports. To keep a focus on the underlying age effects we model a generalized heterosexual population with average risks (i.e., no MSM, no PWIDs, no sex workers) and no entry of HIV+ people from other regions. The model assumes that most people (default 95%, range in variant simulations 60-95%) are "linkable"; i.e., could get linked to effective care given sufficient resources. To simplify the accounting, we assume a rapid jump in the number of people receiving treatment at the start of the TasP campaign, followed by a 2% annual increase that continues until all linkable HIV+ people have been treated. Under historical scenarios of CD4-based targeted ART allocation and current policies of untargeted (random) ART allocation, our model predicts that viral replication would need to be suppressed in 60-85% of infected people at the start of the TasP campaign to drive incidence to negligible levels. Under age-based strategies, by contrast, this percentage dropped by 18-54%, depending on the strength of the epidemic and the age target. For our baseline model, targeting those under age 30 halved the number of people who need to be treated. Age-based targeting also minimized total and time-discounted AIDS deaths over 25 years. Age-based targeting yielded benefits without being highly exclusive; in a model in which 60% of infected people were treated, ~87% and ~58% of those initiating therapy during a campaign targeting those <25 and <30 years, respectively, fell outside the target group. Sensitivity analyses revealed that youth-focused TasP is beneficial due to age-related risk factors (e.g. shorter relationship durations), and an age-specific herd immunity (ASHI) effect that protects uninfected adolescents entering the sexually active population. As testing rates increase in response to UNAIDS 90-90-90 goals, efforts to link all young people to care and treatment could contribute enormously to ending the HIV epidemic.

Sustained Sexual Behavior Change After Acute HIV Diagnosis in Malawi

BACKGROUND

Identification of acute HIV infection (AHI) allows for important opportunities for HIV prevention through behavior change and biomedical intervention. Here, we evaluate changes in sexual risk behaviors among persons with AHI enrolled in a combined behavioral and biomedical intervention designed to reduce onward transmission of HIV.

METHODS

Participants were randomized to standard HIV counseling, a multisession behavioral intervention, or a multisession behavioral intervention plus antiretrovirals. Sexual behaviors were assessed periodically over 1 year.

RESULTS

Four weeks after diagnosis, the predicted probability of reporting multiple sexual partners decreased from 24% to 9%, and the probability of reporting unprotected sex decreased from 71% to 27%. These declines in sexual risk behaviors were sustained over follow-up irrespective of study arm.

CONCLUSIONS

Diagnosis of AHI alone may be sufficient to achieve immediate and sustained behavior change during this highly infectious period.

Perceptions of why Malawians engage in concurrent sexual partnerships among a select population of radio listeners: findings from an exploratory study

Concurrent sexual partnerships have been identified as a potential driver in the HIV epidemic in Southern Africa. This study utilised an innovative approach to explore perceptions of why Malawians may engage in these relationships, and their suggestions for reducing the practice among a select population of radio listeners. Using radio listener feedback in the form of text messages, we analysed approximately 1 000 text messages sent by individuals who listened to a reality radio programme that included real stories, told by Malawians, on topics related to HIV/AIDS. Listeners suggested that lack of satisfaction with one's partner was the overarching reason why individuals had concurrent sexual partnerships. Within the context of lack of satisfaction, listeners cited alcohol use, poor communication and gendered norms as factors related to satisfaction. Listeners suggested that couple communication could increase satisfaction, which, in turn, could reduce concurrent sexual partnerships. Prevention efforts should consider how to utilise couple communication to improve satisfaction as an approach to reduce HIV risk in Southern Africa.

Concurrency and other sexual partnership patterns reported in a survey of young people in rural Northern Tanzania

African adolescents and young adults remain at substantial risk of infection with HIV and other sexually transmitted infections (STIs), and AIDS is the leading cause of death among African adolescents (10–19 years). Sexual partnership patterns influence transmission risk of sexually transmitted infections. We describe patterns reported by youth (15-30y) in a community-based survey in Tanzania. Among participants reporting multiple partners, we investigated factors associated with reported concurrency. Female (N = 6513) and male (N = 7301) participants had median ages of 21 and 22 years, respectively. Most participants (92%) reported having previously been sexually active, of whom 15% of males and <1% of females reported ≥4 partners in the past year. The point prevalence of concurrency was 2.3% (95%CI 1.9–2.9) for females and 10.6% (95%CI 9.3–12.1) for males. High levels of multiple and concurrent partnerships were reported by those previously married. Females were more likely than males to report having spousal/regular partners and longer partnership lengths. Compared to males, the partnerships reported by females were less likely to be new partnerships, and more likely to be defined by the respondent as still ‘ongoing’. Females reporting younger sexual debut were more likely to report concurrent sexual partners. Far fewer young women reported multiple and concurrent partnerships, but we cannot definitively conclude that concurrency was uncommon for women, because stigma towards women’s multiple sexual partnerships might contribute to substantial under-reporting, as was found in extensive qualitative research in the study population. This study provides one of the most comprehensive quantitative descriptions of partnership patterns of young people in an African setting. Interventions addressing sexual risk among youth should involve male partners, empower women to protect themselves within different types of partnerships, and encourage a greater openness about young people’s sexual relationships.

Partnership duration, concurrency, and HIV in sub-Saharan Africa

A widely accepted explanation for the exceptionally high HIV prevalence in sub-Saharan Africa is the practice of long-term overlapping heterosexual partnering. This article shows that long-duration concurrent partnering can be protective against HIV transmission rather than promoting it. Monogamous partnering prevents sexual transmission to anyone outside the partnership and, in an initially concordant-seronegative partnership, prevents sexual acquisition of HIV by either partner. Those protections against transmission and acquisition last as long as the partnership persists without new outside partnerships. Correspondingly, these two protective effects characterise polygynous partnerships, whether or not the polygyny is formal or informal, until a partner initiates a new partnership. Stable and exclusive unions of any size protect against HIV transmission, and more durable unions provide a longer protective effect. Survey research provides little information on partnership duration in sub-Saharan Africa and sheds no light on the interaction of duration, concurrency, and HIV. This article shows how assumptions about partnership duration in individual-based sexual-network models affect the contours of simulated HIV epidemics. Longer mean partnership duration slows the pace at which simulated epidemics grow. With plausible assumptions about partnership duration and at levels of concurrency found in the region, simulated HIV epidemics grow slowly or not at all. Those results are consistent with the hypothesis that long-duration partnering is protective against HIV and inconsistent with the hypothesis that long-term concurrency drives the HIV epidemics in sub-Saharan Africa.

Gender asymmetry in concurrent partnerships and HIV prevalence

The structure of the sexual network of a population plays an essential role in the transmission of HIV. Concurrent partnerships, i.e. partnerships that overlap in time, are important in determining this network structure. Men and women may differ in their concurrent behavior, e.g. in the case of polygyny where women are monogamous while men may have concurrent partnerships. Polygyny has been shown empirically to be negatively associated with HIV prevalence, but the epidemiological impacts of other forms of gender-asymmetric concurrency have not been formally explored. Here we investigate how gender asymmetry in concurrency, including polygyny, can affect the disease dynamics. We use a model for a dynamic network where individuals may have concurrent partners. The maximum possible number of simultaneous partnerships can differ for men and women, e.g. in the case of polygyny. We control for mean partnership duration, mean lifetime number of partners, mean degree, and sexually active lifespan. We assess the effects of gender asymmetry in concurrency on two epidemic phase quantities (R₀ and the contribution of the acute HIV stage to R₀) and on the endemic HIV prevalence. We find that gender asymmetry in concurrent partnerships is associated with lower levels of all three epidemiological quantities, especially in the polygynous case. This effect on disease transmission can be attributed to changes in network structure, where increasing asymmetry leads to decreasing network connectivity.

Sexual Partnership Patterns Among South African Adolescent Girls Enrolled in HPTN [corrected] 068: Measurement Challenges and Implications for HIV/STI Transmission

BACKGROUND

Estimates of sexual partnership durations, gaps between partnerships, and overlaps across partnerships are important for understanding sexual partnership patterns and developing interventions to prevent transmission of HIV/sexually transmitted infections (STIs). However, a validated, optimal approach for estimating these parameters, particularly when partnerships are ongoing, has not been established.

METHODS

We assessed 4 approaches for estimating partnership parameters using cross-sectional reports on dates of first and most recent sex and partnership status (ongoing or not) from 654 adolescent girls in rural South Africa. The first, commonly used, approach assumes all partnerships have ended, resulting in underestimated durations for ongoing partnerships. The second approach treats reportedly ongoing partnerships as right-censored, resulting in bias if partnership status is reported with error. We propose 2 "hybrid" approaches, which assign partnership status to reportedly ongoing partnerships based on how recently girls last had sex with their partner. We estimate partnership duration, gap length, and overlap length under each approach using Kaplan-Meier methods with a robust variance estimator.

RESULTS

Median partnership duration and overlap length varied considerably across approaches (from 368 to 1024 days and 168 to 409 days, respectively), but gap length was stable. Lifetime prevalence of concurrency ranged from 28% to 33%, and at least half of gap lengths were shorter than 6 months, suggesting considerable potential for HIV/STI transmission.

CONCLUSIONS

Estimates of partnership duration and overlap lengths are highly dependent on measurement approach. Understanding the effect of different approaches on estimates is critical for interpreting partnership data and using estimates to predict HIV/STI transmission rates.

Associated Risk Factors of STIs and Multiple Sexual Relationships among Youths in Malawi

BACKGROUND

Having unprotected sex with multiple sexual partners (MSP) is the greatest risk factor for human immunodeficiency virus (HIV) and other sexually transmitted infections (STIs) among youths. Young people with MSPs are less likely to use a condom and the greater the risk for STIs. This study examines the associated risk factors of STIs and multiple sexual partnerships among youths aged 15-24 years.

DATA AND METHODS

The Malawi Demographic Health Survey 2010 data was used. Out of a sample of 2,987 males and 9,559 females aged 15-24 years, 2,026 males and 6,470 females were considered in the study. Chi square test and logistic regression techniques were performed. Analysis was performed using Statistical Package for Social Sciences (SPSS) version 22.

FINDINGS

The results indicate that 1,399 (69.0%) males and 2,290 (35.4%) females reported multiple sexual partnerships (MSP). Within the rural area, females (n = 1779) were more likely to report MSP than males (n = 1082) and within the urban areas, a higher proportion of females (n = 511) still reported MSP, with males (n = 316). About 78% rural females aged 20-24 years, and about 79% rural males aged 15-19 years reported MSP. The likelihood of MSP was higher among females in the poorest households (OR = 1.31), being married (OR = 5.71) and Catholic males (OR = 1.63), who were married (OR = 1.59). Catholic males (OR = 1.82) in the rural areas, who were married (OR = 1.80) and rural females in the northern region (OR = 1.26) were more likely to have MSP. The odds ratios were higher among urban females in the poorest (OR = 3.45) households who were married (OR = 4.22).

CONCLUSIONS

Having more than one sexual partner increases the risk of STIs and sexuality education programs should be introduced that emphasize the danger that surrounds MSP.

Concurrency can drive an HIV epidemic by moving R0 across the epidemic threshold

OBJECTIVE

The objective of this study is to investigate whether concurrency can drive an HIV epidemic by moving R0 across the epidemic threshold.

DESIGN AND METHODS

We use a mathematical framework for a dynamic partnership network and the spread of a one-stage infection to study how concurrency is related to the basic reproduction number R0. Two concurrency indices were used to measure the level of concurrency. The model allows varying the level of concurrency in the population, while other key network properties such as partnership duration and lifetime number of partners are kept fixed. In this way, the effect of concurrency on R0 is investigated as an isolated phenomenon.

RESULTS

We find that an increase in concurrency is associated with an increase of R0. For plausible parameter sets for MSM populations, R0 is always above the epidemic threshold of 1. For scenarios that are plausible for sub-Saharan African populations, we show that increasing the level of concurrency can lead to R0 crossing the epidemic threshold. This occurs already at low levels of concurrency. Only a slight shift of the network structure from a purely monogamous population to one wherein individuals are allowed to have at most two partners is enough for this to happen.

CONCLUSION

Concurrency can be a driver of an HIV epidemic in sub-Saharan Africa for low levels of concurrency, although it is not decisive in MSM populations. A small increase in the level of concurrency can lead to R0 crossing the epidemic threshold in a sub-Saharan African setting.

Characteristics of multiple and concurrent partnerships among women at high risk for HIV infection

OBJECTIVES

We examined parameters of sexual partnerships, including respondents' participation in concurrency, belief that their partner had concurrent partnerships (partners' concurrency), and partnership intervals, among the 2099 women in HIV Prevention Trials Network 064, a study of women at high risk for HIV infection, in 10 U.S. communities.

METHODS

We analyzed baseline survey responses about partnership dates to determine prevalence of participants' and partners' concurrency, intervals between partnerships, knowledge of whether recent partners had undergone HIV testing, and intercourse frequency during the preceding 6 months.

RESULTS

Prevalence of participants' and partners' concurrency was 40% and 36%, respectively; 24% respondents had both concurrent partnerships and nonmonogamous partners. Among women with >1 partner and no concurrent partnerships themselves, the median gap between partners was 1 month. Multiple episodes of unprotected vaginal intercourse with ≥2 of their most recent partners was reported by 60% of women who had both concurrent partnerships and nonmonogamous partners, 50% with only concurrent partners and no partners' concurrency, and 33% with only partners' concurrency versus 14% of women with neither type of concurrency (P < 0.0001). Women who had any involvement with concurrency were also more likely than women with no concurrency involvement to report lack of awareness of whether recent partners had undergone HIV testing (participants' concurrency 41%, partners' concurrency 40%, both participants' and partners' concurrency 48%, neither 17%; P < 0.0001).

CONCLUSIONS

These network patterns and short gaps between partnerships may create substantial opportunities for HIV transmission in this sample of women at high risk for HIV infection.

Serial monogamy and biologic concurrency: measurement of the gaps between sexual partners to inform targeted strategies

Having multiple sexual partners concurrently increases the risk of transmission of a sexually transmitted infection. Even if partnerships do not overlap, transmission potential exists when the gap between partnerships is shorter than the remaining infectious period. In the present article, we quantify the gap between partners to assess transmission potential using data collected by a cross-sectional survey of 2,203 genitourinary medicine clinic patients in England in 2009. Questionnaires asked about patients' 3 most recent partnerships. Gaps were calculated as time (days) between the last sexual encounter with a former partner and the first sexual encounter with the next partner. Among 1,875 patients who reported 1 or more partners in the previous 3 months, 47.6% of men and 27.7% of women reported 2 or more partners. Forty-two percent of the gaps were negative (i.e., partnerships that were concurrent); the median gaps were -7 and -17 days for men and women, respectively (i.e., overlaps were 7 and 17 days for men and women, respectively). Although half of the gaps were positive (serially monogamous partnerships), many were of short duration; the median gaps were 14 and 24 days for men and women, respectively. In over half of the gaps, condoms were used inconsistently with one or both partners, and in one-quarter, condoms were never used with either partner. There is thus a high potential for sexually transmitted infections, as even if partnerships are not behaviorally concurrent, they may be biologically concurrent. These data have important implications for designing and targeting effective health promotion messages.

Coital frequency and condom use in monogamous and concurrent sexual relationships in Cape Town, South Africa

Introduction

A decreased frequency of unprotected sex during episodes of concurrent relationships may dramatically reduce the role of concurrency in accelerating the spread of HIV. Such a decrease could be the result of coital dilution – the reduction in per-partner coital frequency from additional partners – and/or increased condom use during concurrency. To study the effect of concurrency on the frequency of unprotected sex, we examined sexual behaviour data from three communities with high HIV prevalence around Cape Town, South Africa.

Methods

We conducted a cross-sectional survey from June 2011 to February 2012 using audio computer-assisted self-interviewing to reconstruct one-year sexual histories, with a focus on coital frequency and condom use. Participants were randomly sampled from a previous TB and HIV prevalence survey. Mixed effects logistic and Poisson regression models were fitted to data from 527 sexually active adults reporting on 1210 relationship episodes to evaluate the effect of concurrency status on consistent condom use and coital frequency.

Results

The median of the per-partner weekly average coital frequency was 2 (IQR: 1–3), and consistent condom use was reported for 36% of the relationship episodes. Neither per-partner coital frequency nor consistent condom use changed significantly during episodes of concurrency (aIRR=1.05; 95% confidence interval (CI): 0.99–1.24 and aOR=1.01; 95% CI: 0.38–2.68, respectively). Being male, coloured, having a tertiary education, and having a relationship between 2 weeks and 9 months were associated with higher coital frequencies. Being coloured, and having a relationship lasting for more than 9 months, was associated with inconsistent condom use.

Conclusions

We found no evidence for coital dilution or for increased condom use during concurrent relationship episodes in three communities around Cape Town with high HIV prevalence. Given the low levels of self-reported consistent condom use, our findings suggest that if the frequency of unprotected sex with each of the sexual partners is sustained during concurrent relationships, HIV-positive individuals with concurrent partners may disproportionately contribute to onward HIV transmission.

HIV infection and sexual partnerships and behaviour among adolescent girls in Nairobi, Kenya

Early sexual partnerships place young women in sub-Saharan Africa at high risk for HIV. Few studies have examined both individual- and partnership-level characteristics of sexual relationships among adolescent girls. A cross-sectional survey of sexual history and partnerships was conducted among 761 adolescent girls aged 15-19 years in Nairobi, Kenya. Rapid HIV testing was conducted and correlates of HIV infection were determined using multivariate logistic regression. The HIV prevalence was 7% and seropositive adolescents had a younger age at sexual debut (P < 0.01), more sexual partners in 12 months (P = 0.03), and were more likely to report transactional or non-consensual sex (P < 0.01). Girls who reported not knowing their partner's HIV status were 14 times as likely to be HIV-seropositive than girls who knew their partner's status (adjusted odds ratio: 14.2 [1.8, 109.3]). Public health messages to promote HIV testing and disclosure within partnerships could reduce sexual risk behaviours and HIV transmission among adolescents.

Measuring and modelling concurrency

This article explores three critical topics discussed in the recent debate over concurrency (overlapping sexual partnerships): measurement of the prevalence of concurrency, mathematical modelling of concurrency and HIV epidemic dynamics, and measuring the correlation between HIV and concurrency. The focus of the article is the concurrency hypothesis - the proposition that presumed high prevalence of concurrency explains sub-Saharan Africa's exceptionally high HIV prevalence. Recent surveys using improved questionnaire design show reported concurrency ranging from 0.8% to 7.6% in the region. Even after adjusting for plausible levels of reporting errors, appropriately parameterized sexual network models of HIV epidemics do not generate sustainable epidemic trajectories (avoid epidemic extinction) at levels of concurrency found in recent surveys in sub-Saharan Africa. Efforts to support the concurrency hypothesis with a statistical correlation between HIV incidence and concurrency prevalence are not yet successful. Two decades of efforts to find evidence in support of the concurrency hypothesis have failed to build a convincing case.

The role of acute and early HIV infection in the spread of HIV and implications for transmission prevention strategies in Lilongwe, Malawi: a modelling study

BACKGROUND

HIV transmission risk is higher during acute and early HIV infection than it is during chronic infection, but the contribution of early infection to the spread of HIV is controversial. We estimated the contribution of early infection to HIV incidence in Lilongwe, Malawi, and predict the future effect of hypothetical prevention interventions targeted at early infection only, chronic infection only, or both stages.

METHODS

We developed a deterministic mathematical model describing heterosexual HIV transmission, informed by detailed behavioural and viral-load data collected in Lilongwe. We included sexual contact within and outside of steady pairs and divided the infectious period into intervals to allow for changes in transmissibility by infection stage. We used a Bayesian melding approach to fit the model to HIV prevalence data collected between 1987 and 2005 at Lilongwe antenatal clinics. We assessed interventions that reduced the per-contact transmission probability to 0.00003 in people receiving them, and varied the proportion of individuals receiving the intervention in each stage.

FINDINGS

We estimated that 38.4% (95% credible interval 18.6-52.3) of HIV transmissions in Lilongwe are attributable to sexual contact with individuals with early infection. Interventions targeted at only early infection substantially reduced HIV prevalence, but did not lead to elimination, even with 100% coverage. Interventions targeted at only chronic infections also reduced HIV prevalence, but coverage levels of 95-99% were needed for the elimination of HIV. In scenarios with less than 95% coverage of interventions targeted at chronic infections, additional interventions reaching 25-75% of individuals with early infection reduced HIV prevalence substantially.

INTERPRETATION

Our results suggest that early infection plays an important part in HIV transmission in this sub-Saharan African setting. Without near-complete coverage, interventions during chronic infection will probably have incomplete effectiveness unless complemented by strategies targeting individuals with early HIV infection.

FUNDING

National Institutes of Health, University of North Carolina Center for AIDS Research.