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With optimal strategy, human papillomavirus (HPV) vaccines have the potential to control HPV. We have assessed vaccine efficacy (VE), herd effect (HE) of HPV vaccination and overall protective effectiveness (PE) against high-risk HPV infections by HPV type and vaccination strategy in a community-randomized trial using the bivalent HPV16/18 vaccine. We randomized 33 communities to gender-neutral HPV vaccination (Arm A), HPV vaccination of girls and hepatitis B-virus (HBV) vaccination of boys (Arm B) and gender-neutral HBV vaccination (Arm C). Entire 1992-1995 male (40,852) and female (39,420) birth cohorts were invited, and 11,662 males and 20,513 females vaccinated with 20-30% and 45% coverage in 2007-2010. During 2010-2014, 11,396 cervicovaginal samples were collected from 13,545 18.5-year-old attendees. HPV typing was performed by a high-throughput PCR. VE was calculated for HPV vaccinated women and HE for non-HPV-vaccinated women, using the HBV vaccinated, for HE all non-HPV vaccinated, Arm C women as controls. PE was calculated as coverage rate-weighted mean of VE + HE. HPV16/18/45 and 31/33/35 VEs varied between 86-94% and 30-66%, respectively. Only the gender-neutral vaccination provided significant HEs against HPV18 (61%) and HPV31 (72%) in the 1995 birth cohort-increased HEs against HPV33 (39%) and HPV35 (42%) were also observed. Due to the increased HEs, PEs for HPV16/18/45 and HPV31/33/35 were comparable in the gender-neutral arm 1995 birth cohort. High vaccine efficacy against HPV16/18/45 and, gender-neutral vaccination-enforced, herd effect against HPV18/31/33/35 by the bivalent vaccine rapidly provides comparable overall protective effectiveness against six oncogenic HPV types: 16/18/31/33/35/45.

Efficacy of human papillomavirus (HPV) vaccines promises to control HPV infections. However, HPV vaccination programs may lay bare an ecological niche for non-vaccine HPV types. We evaluated type-replacement by HPV type and vaccination strategy in a community-randomized trial executed in HPV vaccination naive population. Thirty-three communities were randomized to gender-neutral vaccination with AS04-adjuvanted HPV16/18 vaccine (Arm A), HPV vaccination of girls and hepatitis B-virus (HBV) vaccination of boys (Arm B) and gender-neutral HBV vaccination (Arm C). Resident 1992-95 born boys (40,852) and girls (39,420) were invited. 11,662 boys and 20,513 girls were vaccinated with 20–30% and 45–48% coverage, respectively. HPV typing of 11,396 cervicovaginal samples was performed by high throughput PCR. Prevalence ratios (PR) between arms and ranked order of HPV types and odds ratio (OR) for having multiple HPV types in HPV16 or 18/45 positive individuals were calculated. The ranked order of HPV types did not significantly differ between arms or birth cohorts. For the non-HPV vaccinated 1992–1993 birth cohorts increased PR, between the gender-neutral intervention versus control arms for HPV39 (PRA 1.84, 95% CI 1.12–3.02) and HPV51 (PRA 1.56, 95% CI 1.11–2.19) were observed. In the gender-neutral arm, increased clustering between HPV39 and the vaccine-covered HPV types 16 or 18/45 (ORA16 = 5.1, ORA18/45 = 11.4) was observed in the non-HPV vaccinated 1994–1995 birth cohorts. Comparable clustering was seen between HPV51 and HPV16 or HPV18/45 (ORB16 = 4.7, ORB18/45 = 4.3), in the girls-only arm. In conclusion, definitively consistent postvaccination patterns of HPV type-replacement were not observed. Future occurrence of HPV39 and HPV51 warrant investigation.

Background Human papillomavirus (HPV) vaccination of girls with very high (>90%) coverage has the potential to eradicate oncogenic HPVs, but such high coverage is hard to achieve. However, the herd effect (HE) depends both on the HPV type and the vaccination strategy. Methods We randomized 33 Finnish communities into gender-neutral HPV16/18 vaccination, girls-only HPV16/18 vaccination, and hepatitis B virus vaccination arms. In 2007–2010, 11 662 of 20 513 of 40 852 of 39 420 resident boys/girls from 1992 to 1995 birth cohorts consented. In 2010–2014, cervicovaginal samples from vaccinated and unvaccinated girls at age 18.5 years were typed for HPV6/11/16/18/31/33/35/39/45/51/52/56/58/59/66/68. Vaccine efficacy for vaccinated girls, HE for unvaccinated girls, and the protective effectiveness (PE) for all girls were estimated. We extended the community-randomized trial results about vaccination strategy with mathematical modeling to assess HPV eradication. Results The HE and PE estimates in the 1995 birth cohort for HPV18/31/33 were significant in the gender-neutral arm and 150% and 40% stronger than in the girls-only arm. Concordantly, HPV18/31/33 eradication was already predicted in adolescents/young adults in 20 years with 75% coverage of gender-neutral vaccination. With the 75% coverage, eventual HPV16 eradication was also predicted, but only with the gender-neutral strategy. Conclusions Gender-neutral vaccination is superior for eradication of oncogenic HPVs.

Background: The risk of acquiring HIV from a single sexual contact varies enormously reflecting biological and behavioural characteristics of both infected and uninfected partners. Accurate information on HIV transmission risk is required to construct evidence-based risk reduction practices for individuals, to direct the provision of prevention strategies at the population level, and enable the definition, quantification and comparison of true exposure in individuals termed 'exposed uninfected' within clinical trials. Methods: Following a systematic review of current literature on HIV transmission estimates, an HIV risk score was developed, incorporating weighted risk factors into a Bernoulli mathematical model, allowing quantification of overall risk of HIV acquisition within HIV-serodiscordant partnerships. Results: The HIV risk score enumerates the relative risk of HIV acquisition from HIV-positive partners incorporating the type and frequency of specific sex acts, the index case HIV plasma viral load and stage of disease, and the presence of genital ulcer disease in either partner and pregnancy, HSV-2 seropositivity, and circumcision status (men only) in the HIV-negative partner. Conclusion: Key determinants of HIV exposure risk can be incorporated into a mathematical model in order to quantify individual relative risks of HIV acquisition. Such a model can facilitate comparisons within clinical trials of exposed uninfected individuals and facilitate interventions to reduce HIV transmission.

A model representing carcinogenic HPV infection transmission dynamics and cervical cancer natural history was adapted to assess the consequences of introducing vaccination against HPV-16 infection. Alternative scenarios either allowing repeated infections with the HPV-16 (i.e. SIS scenario) or assuming that clearance of infection occurs through the development of a long lasting, specific immune response which protects against re-infection (i.e. SIR scenario) were investigated. The difference in reduction in lifetime cervical cancer achieved through vaccination of 12-year-old girls, between SIS and SIR scenarios, was up to 25% of expected cases in an unscreened population. This difference increased to 30% when vaccination of 12-year-old boys was also included as an intervention. The role of SIS or SIR dynamics should be accounted for in the assessment of model-based projections of the effectiveness of vaccination programmes, until available data about the transmission dynamics support the accuracy of model predictions.

Objective To determine how the risk of HIV transmission from homosexual men receiving antiretroviral treatment is related to patterns of patient monitoring and condom use. Methods A stochastic mathematical simulation model was developed of cohorts of men in the Netherlands who have sex with men (MSM), defining the parameters of the model using observational cohort data. The model incorporates viral load trends during first-line treatment, patient monitoring and different scenarios for the way in which condom use may depend on recent viral load measurements. The model does not include the effect of sexually transmitted infections on HIV transmission. Results For MSM receiving treatment, the risk of transmitting HIV to their long-term partner is 22% (uncertainty interval: 9–37%) if condoms are never used. With incomplete use (in 30% of sex acts) the risk is reduced slightly, to 17% (7–29%). However, the risk is as low as 3% (0.2–8%) when men receiving treatment use condoms only 6 months beyond their last undetectable viral load measurement. The risk is further reduced when 3 months is the time period beyond which condoms are used. Conclusions When condom use by HIV-infected men receiving combination treatment with antiretroviral agents is based on their last viral load measurement, the transmission risk is much lower than with incomplete condom use. The key message for patients is that although always using condoms during treatment is the best way to protect partners from the risk of HIV transmission, when such use cannot be achieved, the second best strategy is to use condoms whenever the last undetectable viral load was measured more than 3 months ago.

BACKGROUND: It has been suggested that a new strategy for HIV prevention, 'Universal Test and Treat', whereby everyone is tested for HIV once a year and treated immediately with antiretroviral therapy (ART) if they are infected, could 'eliminate' the epidemic and reduce ART costs in the long term. METHODS: We investigated the impact of test-and-treat interventions under a variety of assumptions about the epidemic using a deterministic mathematical model. RESULTS: Our model shows that such an intervention can substantially reduce HIV transmission, but that impact depends crucially on the epidemiological context; in some situations, less aggressive interventions achieve the same results, whereas in others, the proposed intervention reduces HIV by much less. It follows that testing every year and treating immediately is not necessarily the most cost-efficient strategy. We also show that a test-and-treat intervention that does not reach full implementation or coverage could, perversely, increase long-term ART costs. CONCLUSION: Interventions that prevent new infections through ART scale-up may hold substantial promise. However, as plans move forward, careful consideration should be given to the nature of the epidemic and the potential for perverse outcomes.

Aim: Cervical cancer incidence and mortality have decreased for the last 20 years in Austria; however, they remain relatively high in comparison to other European countries. Screening quality has been suboptimal. In this paper we aim to predict the population-wide long-term effects on cervical cancer morbidity and mortality after introducing an HPV vaccination for 12-year-old girls (and boys) in addition to current screening in comparison with screening only. Methods: Health effects are predicted by a dynamic transmission model that was previously applied in the UK and the Norwegian contexts and validated for Austria. Outcomes analyzed are restricted to cervical cancer mortality and morbidity, which are predicted until 2060 assuming a coverage rate between 65% and 85%, a duration of protection between 10 years and lifelong, and a vaccine efficacy between 80% and 100% in the base case and best case, respectively. Additionally, implications for cancer epidemiology until 2088 are estimated. Results: Compared to screening only, screening plus vaccination of 12-year-old girls (and boys) would result in a median reduction of 10% (15%) fewer new cancer cases and 13% (20%) fewer cervical cancer deaths under best case assumptions over 52 years in the overall female population. In 2060, female population-based incidence and mortality would decrease by 27% and 43%, respectively, when vaccinating girls only and by 37% and 45% when additionally vaccinating boys. After 2060, a continuous further decrease in incidence and mortality can be expected with a maximum of minus 43% and 53%, respectively, in 2088 when vaccinating girls only. Conclusion: Although a constant decrease in cervical cancer incidence and mortality is to be expected after introducing a population-wide HPV vaccination program in Austria, the reduction predicted by this model is lower than expected from clinical trials. This is due to several factors, such as low coverage rate and the long time horizon required for generating the maximum benefit of the vaccination in the overall population. In the context of limited resources, for further reducing cervical cancer in Austria, HPV vaccination programs need to be weighed against other public health alternatives such as improving screening quality.

Background Determining whether interventions to reduce HIV transmission have worked is essential, but complicated by the potential for generalised epidemics to evolve over time without individuals changing risk behaviour. We aimed to develop a method to evaluate evidence for changes in risk behaviour altering the course of an HIV epidemic. Methods We developed a mathematical model of HIV transmission, incorporating the potential for natural changes in the epidemic as it matures and the introduction of antiretroviral treatment, and applied a Bayesian Melding framework, in which the model and observed trends in prevalence can be compared. We applied the model to Zimbabwe, using HIV prevalence estimates from antenatal clinic surveillance and house-hold based surveys, and basing model parameters on data from sexual behaviour surveys. Results There was strong evidence for reductions in risk behaviour stemming HIV transmission. We estimate these changes occurred between 1999 and 2004 and averted 660,000 (95% credible interval: 460,000–860,000) infections by 2008. Discussion The model and associated analysis framework provide a robust way to evaluate the evidence for changes in risk behaviour affecting the course of HIV epidemics, avoiding confounding by the natural evolution of HIV epidemics.

Background: Clandestine induced abortions are a public health problem in many developing countries where access to abortion services is legally restricted. We estimated the prevalence and incidence of, and risk factors for, clandestine induced abortions in a Latin American country. Methods: We conducted a large population-based survey of women aged 18–29 years in 20 cities in Peru. We asked questions about their history of spontaneous and induced abortions, using techniques to encourage disclosure. Results: Of 8242 eligible women, 7992 (97.0%) agreed to participate. The prevalence of reported induced abortions was 11.6% (95% confidence interval [CI] 10.9%–12.4%) among the 7962 women who participated in the survey. It was 13.6% (95% CI 12.8%–14.5%) among the 6559 women who reported having been sexually active. The annual incidence of induced abortion was 3.1% (95% CI 2.9%–3.3%) among the women who had ever been sexually active. In the multivariable analysis, risk factors for induced abortion were higher age at the time of the survey (odds ratio [OR] 1.11, 95% CI 1.07–1.15), lower age at first sexual intercourse (OR 0.87, 95% CI 0.84–0.91), geographic region (highlands: OR 1.56, 95% CI 1.23–1.97; jungle: OR 1.81, 95% CI 1.41–2.31 [v. coastal region]), having children (OR 0.82, 95% CI 0.68–0.98), having more than 1 sexual partner in lifetime (2 partners: OR 1.61, 95% CI 1.23–2.09; ≥ 3 partners: OR 2.79, 95% CI 2.12–3.67), and having 1 or more sexual partners in the year before the survey (1 partner: OR 1.36, 95% CI 1.01–1.72; ≥ 2 partners: OR 1.54, 95% CI 1.14–2.02). Overall, 49.0% (95% CI 47.6%–50.3%) of the women who reported being currently sexually active were not using contraception. Interpretation: The incidence of clandestine, potentially unsafe induced abortion in Peru is as high as or higher than the rates in many countries where induced abortion is legal and safe. The provision of contraception and safer-sex education to those who require it needs to be greatly improved and could potentially reduce the rate of induced abortion.

Background Cervical cancer, although usually preventable by Pap smear screening, remains the leading cause of cancer-related deaths among women in Peru. The percentages and characteristics of women in Peru who have or have not had a Pap smear have not been defined. Methods In an urban community randomized trial of sexually transmitted infection (STI)/HIV prevention in Peru, 6712 randomly selected women between the ages of 18 and 29 from 20 cities were interviewed regarding having had cervical Pap smears. Results Among women sampled, only 30.9% had had a Pap smear. By multivariate analysis, the main predictors of having a Pap smear were having had sex, having had children, completion of secondary education and increasing age. Regional variations were also found: women from the highlands and rainforest were less likely to have had Pap smears than women from the coast. Conclusion A norm of seeking and receiving Pap smears has not been established among sexually active young Peruvian women. To improve Pap smear coverage in Peru, promotion efforts should target underserved women and regions with less coverage.

Background: Sexual behavioural change must lie at the centre of efforts to alleviate the global scourge of HIV/AIDS by preventing new infections. Statistical analysis of risk factors at the individual-level may be used to design behaviour interventions. The importance of reducing cross-generational sex (young women having sex with older men) and delaying age at first sex on the spread of HIV at the population-level has been presumed but not scientifically investigated and quantified. Methods: A mathematical model of heterosexual spread of HIV was developed and used to predict the population-level impact of reducing cross-generational sex, delaying sexual debut and increasing condom use. Results: The impact of behaviour change on the spread of HIV is sensitive to the structure and reaction of the sexual network. Reducing cross-generational sex could have little impact on the risk of infection unless it is accompanied by a reduction in the number of risky sexual contacts; even exclusive peer-to-peer sexual mixing patterns can support high endemic levels of HIV. The benefit of delaying age at sexual debut is comparatively small and is reduced if males continue to prefer young partners or if young women spend more time unmarried. In Manicaland, Zimbabwe condom use by older men is especially low but if they were to use condoms as frequently as young men, the reduction in average risk of infection could exceed that generated by a two-year delay in first sex. Conclusions: At the individual-level avoiding sex with older partners and delaying sexual debut can decrease the risk of infection but at the population- level these interventions may do little to limit the spread of HIV without wider-ranging behavioural changes throughout the sexual network. Mathematical models are essential to explore the population-level impact of individual-level behavioural changes.

Background: Preventing HIV infection is still an essential goal in tackling the HIV/AIDS pandemic. Remarkably little is known about how best to reduce HIV incidence because most trials focus on the reduction of risk behaviours and assume an effect on HIV incidence. Objective: To discuss the evidence for the effectiveness of HIV prevention strategies, exploring the different types of evidence available: individual and community randomised controlled trials, and observational studies. Results: Although providing a gold standard for evidence, trials have been limited in their scope and are difficult to interpret and generalise. There have been examples of national level successes in preventing HIV which have been detected in surveillance data and understood through behavioural and modelling studies. These have the advantage of being to scale and indicating effectiveness rather than efficacy. Conclusions: Although randomised trials are important because of their scientific rigor, it is also important that evidence from observational epidemiology is not overlooked. Only if good quality, consistent data are available can the history of the HIV epidemic be appropriately analysed.

Objectives: This study sought to evaluate the utility of the Determine Syphilis TP test performed in Peruvian commercial sex venues for the detection of active syphilis; and determine the feasibility of integrating rapid syphilis testing for female sex workers (FSW) into existing health outreach services. Methods: We tested 3586 female sex workers for syphilis by Determine in the field using whole blood fingerstick, and by rapid plasma reagin (RPR) and Treponema pallidum haemagglutination assay (TPHA) in a central laboratory in Lima using sera. Results: 97.4% of the FSW offered rapid syphilis testing participated; and among those who tested positive, 87% visited the local health centre for treatment. More than twice as many specimens were RPR reactive using serum in Lima (5.7%) than tested positive by whole blood Determine in the field (2.8%), and although most were confirmed by TPHA, only a small proportion (0.7%) were RPR reactive at >1:8 dilutions, and likely indicating active syphilis. Sensitivity, specificity and positive predictive value of the Determine Syphilis TP test in whole blood when compared to serum RPR reactivity at any dilution confirmed by TPHA as the gold standard were 39.3%, 99.2% and 71.4%, respectively. Sensitivity improved to 64.0% when using serum RPR >1:8 confirmed by TPHA. Invalid tests were rare (0.3%). Conclusions: Rapid syphilis testing in sex work venues proved feasible, but Determine using whole blood obtained by fingerstick was substantially less sensitive than reported in previous laboratory-based studies using serum. Although easy to perform in outreach venues, the utility of this rapid syphilis test was relatively low in settings where a large proportion of the targeted population has been previously tested and treated.

The incidence of diagnosed HIV in the UK is increasing. We calculated the incidence-to-prevalence ratio, IPR(t), which must exceed an 'epidemic threshold', the reciprocal of the mean infectious period, for sustained transmission to occur. For heterosexuals the IPR(t) is too low for a self-sustained UK epidemic, and incidence is driven by increasing prevalence, mostly from imported cases. For men who have sex with men the IPR(t) is around the epidemic threshold, suggesting that spread is not yet under control.

Heterosexual transmission has long been considered the predominant route of transmission of HIV-1 in sub-Saharan Africa. However some have argued that unsafe medical injections account for the majority of transmission in this region. The goal of this study was to compare the HIV-1 epidemics associated with different transmission routes. An age-structured deterministic compartmental model of HIV-1 transmission through both sexual contact and unsafe injections was developed and simulations of sexual transmission and iatrogenic transmission were compared with observed prevalence. Iatrogenic transmission probabilities and numbers of unsafe injections required to generate observed prevalence are unfeasibly high. Simulations of sexually transmitted HIV-1 generate observed prevalence using transmission probabilities and average partner change rates that are within plausible bounds. Heterosexual transmission seems a more likely route of transmission in the region. However heterogeneity in contact patterns is of key importance. Further information on groups who are likely to receive more injections is required. (authors)

OBJECTIVE: To compare alternative methods to vital registration systems for estimating adult mortality, and describe patterns of mortality in Manicaland, Zimbabwe, which has been severely affected by HIV. METHODS: We compared estimates of adult mortality from (1) a single question on household mortality, (2) repeated household censuses, and (3) an adult cohort study with linked HIV testing from Manicaland, with a mathematical model fitted to local age-specific HIV prevalence (1998 -2000). FINDINGS: The crude death rate from the single question (29 per 1000 person-years) was roughly consistent with that from the mathematical model (22 -25 per 1000 person-years), but much higher than that from the household censuses (12 per 1000 person-years). Adult mortality in the household censuses (males 0.65; females 0.51) was lower than in the cohort study (males 0.77; females 0.57), while mathematical models gave a much higher estimate, especially for females (males 0.80 -0.83; females 0.75 -0.80). The population attributable fraction of adult deaths due to HIV was 0.61 for men and 0.70 for women, with life expectancy estimated to be 34.3 years for males and 38.2 years for females. CONCLUSION: Each method for estimating adult mortality had limitations in terms of loss to follow-up (cohort study), under-ascertainment (household censuses), transparency of underlying processes (single question), and sensitivity to parameterization (mathematical model). However, these analyses make clear the advantages of longitudinal cohort data, which provide more complete ascertainment than household censuses, highlight possible inaccuracies in model assumptions, and allow direct quantification of the impact of HIV.

This paper reviews the data sources and methods used to estimate the number of people on, and coverage of, antiretroviral therapy (ART) programmes in low- and middle-income countries and to monitor the progress towards the "3 by 5" target set by WHO and UNAIDS. We include a review of the data sources used to estimate the coverage of ART programmes as well as the efforts made to avoid double counting and over-reporting. The methods used to estimate the number of people in need of ART are described and expanded with estimates of treatment needs for children, both for ART and for cotrimoxazole prophylaxis. An estimated 6.5 million people were in need of treatment in low- and middle-income countries by the end of 2004, including 660 000 children under age 15 years. The mid-2005 estimate of 970 000 people receiving ART in low- and middle-income countries (with an uncertainty range 840 000-1 100 000) corresponds to a coverage of 15% of people in need of treatment.

Prompt treatment of infectious diseases plays an important role in infection control. In the face of the increasing incidence of sexually transmitted infection, the ability of genitourinary medicine services to provide appropriate and timely care is reduced. To explore the relationship between capacity and demand for care, we developed and analyzed a mathematical model of gonorrhea transmission, incorporating patient flow through treatment services and heterogeneity in sexual risk behavior. Two equilibrium levels of infection incidence--"high" and "low"--exist for the same parameter values, and which of them occurs depends on starting conditions. At the high-incidence equilibrium, there is a "vicious circle" in which inadequate treatment capacity leads to many untreated infections, generating further high incidence and high demand and thus maintaining the inadequacy of services. A substantial increase in capacity is needed to interrupt this process and enter a "virtuous circle," in which adequate service provision keeps demand low, offering cost savings as well as improvements in health.

Observational studies examining the effects of other sexually transmitted diseases (STDs) on HIV susceptibility differ in the populations observed and in which "other STDs" are examined. The extent to which an STD alters the risk of transmission of HIV may vary according to disease and population characteristics.The goals of this study were to review studies examining the effect of other STDs on HIV-1 susceptibility and to correlate their effect estimates with type of "other STD", study design, and population characteristics.Relevant studies with longitudinal design were identified through a systematic search of the PubMed database, and their evidence was critically evaluated. Metaregression techniques were then used to correlate study characteristics with corresponding effect estimates.Of 31 studies included, 4 contained direct data on exposure to HIV-1. Three of these were inconclusive, the fourth indicating a strong relationship between STDs and transmission of HIV. Pooled effect estimates using all studies are statistically significant and indicate a 2- to 3-fold increase in risk of HIV-1 acquisition. Effect estimates corresponding some of the "other STD" categories exhibit heterogeneity, but no significant associations with study characteristics were found.Most of the studies lack direct exposure data, lending them susceptible to exposure bias. Another problem may be measurement error about risk factors and STD status at time of HIV-1 infection. Because direct exposure data are difficult to come by (4 of 31 studies contained such data, all but 1 inconclusive), future observational studies on the influence of STDs on HIV-1 transmission should include quantitative analyses of the sensitivity of results to potential confounding and measurement error if they are to further understanding.

Background: Sexually transmitted infections spread through a network of contacts created by the formation of sexual partnerships. In physics, networks have been characterized as "scale-free" if they follow a power law with an exponent between 2 and 3.Objective: The objective of this study was to test statistically whether distributions of numbers of sexual partners reported from different populations are well described by power laws.Study Design: Power laws and an exponential null model are fitted by maximum likelihood techniques to reported distributions of numbers of partners. Data are taken from 4 population-based surveys, 3 from Britain and I from rural Zimbabwe.Results: The networks can be described by power laws over a number of orders of magnitude. In addition, the derived exponents differ significantly and meaningfully, with an "accelerating network" formed between men who have sex with men (MSM).Conclusions: A scale-free network approach provides a reasonable description of distributions of reported numbers of sexual partners.

Despite worldwide efforts to prevent HIV infection, the number of people affected continues to rise. The authors of this article argue that a commonsense approach based on simple country by country analyses could improve the situation

Sexual transmission of HIV from injection drug users (IDUs) to their non-IDU sex partners has been clearly documented as an important public health issue. The extent to which such ‘first-wave’ sexual HIV transmission will generate HIV epidemics within the wider heterosexual population is of importance for prioritisation, design and targeting of preventive interventions. In Russia, factors which will influence the scale of sexual HIV transmission outwards from IDUs include: (a) HIV prevalence and incidence among IDUs; (b) the extent and patterns of sexual mixing between IDUs and non-IDUs; (c) levels of sexual risk behaviour in these partnerships; (d) sexually transmitted infection (STI) type and prevalence in IDUs and non-IDUs. The size and behaviour of the ‘bridging population’, which interacts with both IDUs and the general population, as well as STI prevalence, sexual mixing patterns and sexual risk behaviour within the general population, will be crucial in determining the scale of heterosexual HIV spread. More empirical research, in conjunction with mathematical modelling of the transmission dynamics of HIV/STIs, is necessary to better understand the role of these factors in determining the nature and extent of HIV epidemics in different contexts. In Russia, there is a current need for research on bridging groups, particularly female IDU sex workers and their male clients, and for implementation of second generation surveillance, including monitoring of HIV/STI rates and risk behaviour in well-defined representative samples from both high risk groups and the general population. The many gaps in currently-available data make precise predictions of the future scale and extent of the HIV epidemic in Russia difficult. Nevertheless, existing evidence suggests that continued rapid spread of HIV among IDUs will occur, and that there is a greater risk of significant diffusion of HIV into and within the heterosexual population than has been seen as a result of IDU-associated epidemics in North America and Western Europe. Effective, high-coverage interventions aimed at simultaneously reducing injecting and sexual risk behaviour among IDUs and sex workers, as well as interventions aimed at the populations which interact with them, particularly clients of sex workers and young people, are urgently required.

Background: To investigate the association between migration and HIV infection among migrant and nonmigrant men and their rural partners. Goal: The goal was to determine risk factors for HIV-1 infection in South Africa. Study Design: This was a cross-sectional study of 196 migrant men and 130 of their rural partners as well as 64 nonmigrant men and 98 rural women whose partners are nonmigrant. Male migrants were recruited at work in two urban centers 100 km and 700 km from their rural homes. Rural partners were traced and invited to participate. Nonmigrant couples were recruited for comparison. The study involved administration of a detailed questionnaire and blood collection for HIV testing. Results: Testing showed that 25.9% of migrant men and 12.7% of nonmigrant men were infected with HIV (P = 0.029; odds ratio = 2.4; 95% CI = 1.1–5.3). In multivariate analysis main risk factors for male HIV infection were being a migrant ever having used a condom and having lived in four or more places during a lifetime. Being the partner of a migrant was not a significant risk factor for HIV infection among women; significant risk factors were reporting more than one current regular partner being younger than 35 years and having STD symptoms during the previous 4 months. Conclusion: Migration is an independent risk factor for HIV infection among men. Workplace interventions are urgently needed to prevent further infections. High rates of HIV were found among rural women and the migration status of the regular partner was not a major risk factor for HIV. Rural women lack access to appropriate prevention interventions regardless of their partners’ migration status. (authors)

Prior to the XIIIth World AIDS Conference in Durban, debate raged in the community over the practicalities, cost and ethics of delivering antiretroviral drugs to the developing world. Two years on, that discussion is history. Political and financial forces will now deliver these drugs to such nations. How then can we expect their arrival to alter the HIV landscape?

Background: our understanding of human papilloma virus (HPV) and cervical cancer has improved dramatically, with a vaccine against the viral infection being a real possibility in the near future. Aims: the goal of an HPV vaccine would be to reduce the prevalence of infection and hence the risk of cervical abnormalities. However, questions arise as to how this would interact with an existing intervention, screening, which reduces the progress of cervical abnormalities to serious disease. Furthermore, will a vaccine against one genotype influence the other types within a population and will the patterns of infection and disease remain the same if the vaccine alters the timing and type of HPVs experienced within a population? What would a vaccine that only worked in one sex achieve and how widespread would the use of such a vaccine have to be? Conclusion: the above-given questions can be addressed within a theoretical framework that describes the transmission dynamics of human papilloma virus.

An age structured model of heterosexual HIV‐1 transmission is used to explore the impact of observed patterns of fertility on measures of HIV prevalence derived from child bearing women. Observed reductions in fertility caused by women being outside sexual unions before the age of 20 years, the influence of bacterial sexually transmitted infections and the influence of HIV associated morbidity are all included in the model. We illustrate how the biases in prevalence estimates for a localised epidemic can change with time since the start of the epidemic. As the average age of HIV infected women increases, the over‐estimate of prevalence from antenatal clinic samples first increases and then declines. This works in opposition to the influence of HIV‐1 on fertility, which causes HIV‐1 prevalence to be under‐estimated initially. Additionally a reduction in fertility associated with bacterial infection in the highest sexual activity classes causes a substantial under‐estimate of HIV prevalence initially, but w...

Although the national rate of gonorrhea declined 68% from 1975 to 1995, rates remain high in many inner-city areas. In 1995, the gonorrhea rate in Newark, NJ, was five times the US rate.To determine factors associated with acquisition of gonorrhea by men in Newark.A case-control study conducted at the sexually transmitted disease (STD) clinic in Newark, comparing males 15 to 29 years with culture-confirmed gonorrhea to controls with no STD.Compared with controls, males with gonorrhea more frequently reported at least 1 casual sex partner within the preceding month (adjusted odds ratio [OR], 3.2; 95% CI, 1.8-5.7), sex after using marijuana during the preceding month (OR, 2.4; 95% CI, 1.1-5.3), and a history of incarceration (OR, 2.1; 95% CI, 1.2-3.7). Of males with casual partners, having a new casual sexual relationship (onset within the past month) was particularly risky for gonorrhea (OR, 3.9; 95% CI, 1.2-12.7). Incorrect condom use was highly prevalent for both cases and controls. Many persons with gonorrhea reported that they were not willing to consistently use condoms or to have only one partner.Sex with casual partners is associated with gonorrhea in males, and may be a difficult practice to change. Condoms are often used incorrectly, if at all, in this population. Prevention strategies, in addition to the promotion of condom use and monogamy, may be necessary.

Summary Theoretical results indicate that extensive coverage with low efficacy type 1 human immunodeficiency virus (HIV) vaccines could substantially reduce the incidence of HIV in developing countries. There is a non-linear relationship between effective vaccine coverage and HIV prevalence such that improved efficacy brings diminishing returns. The relative contribution of HIV-associated mortality and behavioural heterogeneity to this non-linear relationship is explored using deterministic mathematical models. If the duration of risk of acquiring HIV is long relative to the HIV incubation period then infection-associated mortality can generate the non-linear relationship. However, in its absence the same relationship results from behavioural heterogeneity. Models of HIV vaccination alongside other interventions generate qualitative results that suggest that targeted interventions lead to less redundancy in control efforts.

Summary Patterns of sexual mixing and the sexual partner network are important determinants of the spread of all sexually transmitted diseases (STDs), including the human immunodeficiency virus. Novel statistical problems arise in the analysis and interpretation of studies aimed at measuring patterns of sexual mixing and sexual partner networks. Samples of mixing patterns and network structures derived from randomly sampling individuals are not themselves random samples of measures of partnerships or networks. In addition, the sensitive nature of questions on sexual activity will result in the introduction of non-response biases, which in estimating network structures are likely to be non-ignorable. Adjusting estimates for these biases by using standard statistical approaches is complicated by the complex interactions between the mechanisms generating bias and the non-independent nature of network data. Using a two-step Monte Carlo simulation approach, we have shown that measures of mixing patterns and the network structure that do not account for missing data and non-random sampling are severely biased. Here, we use this approach to adjust raw estimates in data to incorporate these effects. The results suggest that the risk for transmission of STDs in empirical data is underestimated by ignoring missing data and non-random sampling.

A strong, global commitment to expanded prevention programs targeted at sexual transmission and transmission among injecting drug users, started now, could avert 28 million new HIV infections between 2005 and 2015. This figure is more than half of the new infections that might otherwise occur during that period in 125 low- and middle-income countries. Although preventing these new infections would require investing about U.S.$122 billion over this period, it would reduce future needs for treatment and care. Our analysis suggests that it will cost about U.S.$3900 to prevent each new infection, but that this will produce a savings of U.S.$4700 in forgone treatment and care costs. Thus, greater spending on prevention now would not only prevent more than half the new infections that would occur from 2005 to 2015 but would actually produce a net financial saving as future costs for treatment and care are averted.

Empirical studies have the potential to collect data on patterns of sexual mixing and network structures.To explore the contribution of different network measures in sexually transmitted disease epidemiology.Individual-based stochastic simulations of a network of sexual partnerships and sexually transmitted disease transmission are analyzed using logistic regression.Measures accumulated over times similar to the duration of infection are more informative than are static cross sections. The patterns of sexual mixing and network structure influence patterns of infection. In particular, the establishment of infection is most sensitive to the proportion of nonmonogamous pairs, the component distribution and cohesion among those with high activity. The subsequent prevalence is most sensitive to the assortativeness of mixing in the high-activity class and a measure of cohesion, both of which reflect the decrease in prevalence brought about by less widespread connections. A person's risk for infection is determined by local rather than global network structures.

Background: As part of a community-randomized trial of a multicomponent intervention to prevent sexually transmitted infections, we created Mobile Teams (MTs) in ten intervention cities across Peru to improve outreach to female sex workers (FSW) for strengthened STI prevention services. Methods: Throughout 20 two-month cycles, MTs provided counseling; condoms; screening and specific treatment for Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT), and vaginal Trichomonas vaginalis (TV) infections; and periodic presumptive metronidazole treatment for vaginal infections. Results: MTs had 48,207 separate encounters with 24,814 FSW; numbers of sex work venues and of FSW reached increased steadily over several cycles. Approximately 50% of FSW reached per cycle were new. Reported condom use with last client increased from 73% to 93%. Presumptive metronidazole treatment was accepted 83% of times offered. Over 38 months, CT prevalence declined from 15·4% to 8·2%, and TV prevalence from 7·3% to 2·6%. Among participants in ≥9 cycles, CT prevalence decreased from 12·9% to 6·0% (p

The impact of transmission events from patients with shingles (zoster) on the epidemiology of varicella is examined before and after the introduction of mass immunization by using a stochastic mathematical model of transmission dynamics. Reactivation of the virus is shown to damp stochastic fluctuations and move the dynamics toward simple annual oscillations. The force of infection due to zoster cases is estimated by comparison of simulated and observed incidence time series. The presence of infectious zoster cases reduces the tendency for mass immunization to increase varicella incidence at older ages when disease severity is typically greater.