Population migration and the spread of types 1 and 2 human immunodeficiency viruses

Mobility and HIV vulnerabilities among female sex workers in Guinea-Bissau: findings from an integrated bio-behavioral survey

BACKGROUND

Mobility is an important risk determinant for HIV given the potential for intermittent access to HIV services. Mobility may be particularly relevant among female sex workers, (FSW) who have been shown to be at high risk for HIV in settings around the world. Data regarding the role mobility plays in exacerbating HIV risks among FSW across Sub-Saharan Africa remains limited, and data on FSW in Guinea-Bissau is sparse.

METHODS

FSW in four regions of Guinea-Bissau were recruited with a respondent-driven sampling (RDS) method and participated in an integrated bio-behavioral survey between September 27, 2017 and January 26, 2018. Associations between reported general mobility, mobility to or residence in Bissau, and social and HIV vulnerabilities among FSW in Guinea-Bissau were assessed using multivariable logistic regression models. Population proportions were weighted for RDS sampling, while logistic regression models were not.

RESULTS

Survey respondents included 323 individuals in Bissau, 45 in Bissorã, 140 in Bafatá, and 59 in Gabu. Statistical analyses demonstrated that mobility to more than one destination was significantly associated with recent sex without a condom (ie, sex without a condom within the last three sex acts) with both clients (aOR: 2.47 (95% CI: 1.08, 5.64)) and non-paying partners (aOR: 5.39 (95% CI: 2.61, 11.15)) compared to non-mobility. However, mobility to one or more locations was also associated with higher odds of receiving HIV prevention information, and mobility to more than one location was associated with participating in programming with HIV-related organizations.

CONCLUSIONS

These results suggest that while some prevention services including HIV prevention information reach mobile FSW in Guinea-Bissau more than their non-mobile counterparts, the higher rates of condomless sex among mobile FSW suggest that HIV prevention needs may remain unmet for mobile FSW in Guinea-Bissau. Additionally, the results suggest a nuanced relationship between mobility, place of residence, and HIV and social vulnerabilities and prevention indicators.

Effectiveness of Cash Transfer Delivered Along With Combination HIV Prevention Interventions in Reducing the Risky Sexual Behavior of Adolescent Girls and Young Women in Tanzania: Cluster Randomized Controlled Trial

BACKGROUND

Poverty and social inequality exacerbate HIV risk among adolescent girls and young women (AGYW) in sub-Saharan Africa. Cash transfers can influence the structural determinants of health, thereby reducing HIV risk.

OBJECTIVE

This study assessed the effectiveness of cash transfer delivered along with combination HIV prevention (CHP) interventions in reducing the risky sexual behavior of AGYW in Tanzania. The incidence of herpes simplex virus type 2 (HSV-2) infection was used as a proxy for sexual risk behavior.

METHODS

A cluster randomized controlled trial was conducted in 15 matched pairs of communities (1:1 intervention to control) across 3 strata (urban, rural high-risk, and rural low-risk populations) of the Shinyanga Region, Tanzania. The target population was out-of-school AGYW aged 15-23 years who had completed 10-hour sessions of social and behavior change communication. Eligible communities were randomly assigned to receive CHP along with cash transfer quarterly (intervention group) or solely CHP interventions (control group) with no masking. Study recruitment and baseline survey were conducted between October 30, 2017 and December 1, 2017. Participants completed an audio computer-assisted self-interview, HIV counselling and testing, and HSV-2 testing at baseline and during follow-up visits at 6, 12, and 18 months after the baseline survey. A Cox proportional hazards model with random effects specified at the level of clusters (shared frailty) adjusted for matching pairs and other baseline imbalances was fitted to assess the effects of cash transfer on the incidence of HSV-2 infection (primary outcome). Secondary outcomes included HIV prevalence at follow-up, self-reported intergenerational sex, and self-reported compensated sex. All secondary outcomes were measured at each study visit.

RESULTS

Of the 3026 AGYW enrolled in the trial (1482 in the intervention and 1544 in the control), 2720 AGYW (1373 in the intervention and 1347 in the control) were included in the final analysis. Overall, HSV-2 incidence was not significantly different at all follow-up points between the study arms in the adjusted analysis (hazard ratio 0.96, 95% CI 0.67-1.38; P=.83). However, HSV-2 incidence was significantly lower in the rural low-risk populations who received the cash transfer intervention (hazard ratio 0.45, 95% CI 0.29-0.71; P=.001), adjusted for potential confounders.

CONCLUSIONS

Although this trial showed no significant impact of the cash transfer intervention on HSV-2 incidence among AGYW overall, the intervention significantly reduced HSV-2 incidence among AGYW in rural low-risk communities. Factors such as lesser poverty and more asset ownership in urban and rural high-risk communities may have undermined the impact of cash transfer.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03597243; https://clinicaltrials.gov/show/NCT03597243.

The impact of the caregiver mobility on child HIV care in the Manhiça District, Southern Mozambique: A clinical based study

Introduction

Manhiça District, in Southern Mozambique harbors high HIV prevalence and a long history of migration. To optimize HIV care, we sought to assess how caregiver’s mobility impacts children living with HIV (CLHIV)´s continuation in HIV care and to explore the strategies used by caregivers to maintain their CLHIV on antiretroviral treatment (ART).

Methods

A clinic-based cross-sectional survey conducted at the Manhiça District Hospital between December-2017 and February-2018. We enrolled CLHIV with a self-identified migrant caregiver (moved outside of Manhiça District ≤12 months prior to survey) and non-migrant caregiver, matched by the child age and sex. Survey data were linked to CLHIV clinical records from the HIV care and treatment program.

Results

Among the 975 CLHIV screened, 285 (29.2%) were excluded due to absence of an adult at the appointment. A total of 232 CLHIV-caregiver pairs were included. Of the 41 (35%) CLHIV migrating with their caregivers, 38 (92.6%) had access to ART at the destination because either the caregivers travelled with it 24 (63%) or it was sent by a family member 14 (36%). Among the 76 (65%) CLHIV who did not migrate with their caregivers, for the purpose of pharmacy visits, 39% were cared by their grandfather/grandmother, 28% by an aunt/uncle and 16% by an adult brother/sister. CLHIV of migrant caregivers had a non-statistically significant increase in the number of previous reported sickness episodes (OR = 1.38, 95%CI: 0.79–2.42; p = 0.257), ART interruptions (OR = 1.73; 95%CI: 0.82–3.63; p = 0.142) and lost-to-follow-up episodes (OR = 1.53; 95%CI: 0.80–2.94; p = 0.193).

Conclusions

Nearly one third of the children attend their HIV care appointments unaccompanied by an adult. The caregiver mobility was not found to significantly affect child’s retention on ART. Migrant caregivers adopted strategies such as the transportation of ART to the mobility destination to avoid impact of mobility on the child’s HIV care. However this may have implications on ART stability and effectiveness that should be investigated in rural areas.

Prevalence of Untreated HIV and Associated Risk Behaviors Among the Sexual Partners of Recent Migrants and Long-term Residents in Rakai, Uganda

BACKGROUND

Migrants in sub-Saharan Africa are at increased risk of HIV acquisition after migration, but little is known about their sexual partners at place of destination.

SETTING

Rakai Community Cohort Study (RCCS) in Uganda.

METHODS

From 1999 to 2016, persons aged 15-49 years were surveyed in the RCCS and reported on their 4 most recent sexual partners in the last year. We compared the characteristics of sexual partners reported by migrants moving into RCCS communities in the last 2 years (ie, in-migrants) with those of long-term residents with no recent migration history. Among a subset of participants in cohabitating epidemiologically linked couples of known HIV serostatus, we also assessed prevalence of having ≥1 untreated HIV-positive partner among in-migrants and long-term residents.

RESULTS

One hundred sixteen thousand seven hundred forty-four sexual partners were reported by 29,423 participants. The sexual partnerships of in-migrants were significantly less likely to be marital, more likely to span community boundaries, and shorter in duration than those of long-term residents. In-migrants also reported more sexual partners and were less likely to know their partner's HIV status or to have told their partner their HIV status. Among 7558 epidemiologically linked couples, HIV-negative in-migrants were more likely to partner with untreated HIV-positive persons compared with HIV-negative long-term residents (women: 6.3% vs. 4.1%; prevalence risk ratio = 1.77, 95% confidence interval: 1.49 to 2.11; men: 6.9% vs. 3.9%; prevalence risk ratio = 1.72, 95% confidence interval: 1.38-2.14).

CONCLUSION

There is a higher frequency of risky sexual behaviors among the partnerships of in-migrants compared with those of long-term residents. Among cohabitating couples, in-migrants are more likely to partner with untreated HIV-positive individuals.

Is It the Timing? Short-Term Mobility and Coital Frequency in Agbogbloshie, Ghana

Short-term mobility is often associated with increased sexual risk behavior. Mobile individuals often have higher rates of sexual risk behavior compared to non-mobile individuals, but the reasons why are not clear. Using monthly retrospective panel data from 202 men and 282 women in Agbogbloshie, Ghana, we tested whether short-term mobility was associated with changes in coital frequency, and whether the association was due to the act of travel in the given month (e.g., enabling higher risk behavior), the reason for travel, or an individual's travel propensity at other times in the year. Overnight travel specifically to visit family or friends, or for education, health, or other reasons, was associated with increased coital frequency for men. However, men with higher travel propensities had lower overall coital frequency and the act of traveling enabled more sex only for the most frequent male travelers. Men who seldom traveled had much higher coital frequency, but the act of traveling was not associated with additional sex acts. For women, travel for education, health, or other reasons increased coital frequency. Occasional female travelers had slightly more sex acts compared to non-mobile women, and the act of traveling for these women was associated with slight increases in coital frequency, supporting the enabling hypothesis. Highly mobile women had fewer sex acts per month on average. Our findings suggest that mobility characteristics measured on a broad temporal scale, as well as the reason for mobility, are important to understand the relationship between short-term mobility and sexual behavior.

Migration, hotspots, and dispersal of HIV infection in Rakai, Uganda

HIV prevalence varies markedly throughout Africa, and it is often presumed areas of higher HIV prevalence (i.e., hotspots) serve as sources of infection to neighboring areas of lower prevalence. However, the small-scale geography of migration networks and movement of HIV-positive individuals between communities is poorly understood. Here, we use population-based data from ~22,000 persons of known HIV status to characterize migratory patterns and their relationship to HIV among 38 communities in Rakai, Uganda with HIV prevalence ranging from 9 to 43%. We find that migrants moving into hotspots had significantly higher HIV prevalence than migrants moving elsewhere, but out-migration from hotspots was geographically dispersed, contributing minimally to HIV burden in destination locations. Our results challenge the assumption that high prevalence hotspots are drivers of transmission in regional epidemics, instead suggesting that migrants with high HIV prevalence, particularly women, selectively migrate to these areas.

A method for statistical analysis of repeated residential movements to link human mobility and HIV acquisition

We propose a method for analyzing repeated residential movements based on graphical loglinear models. This method allows an explicit representation of residential presence and absence patterns from several areas without defining mobility measures. We make use of our method to analyze data from one of the most comprehensive demographic surveillance sites in Africa that is characterized by high adult HIV prevalence, high levels of poverty and unemployment and frequent residential changes. Between 2004 and 2016, residential changes were recorded for 8,857 men over 35,500.01 person-years, and for 12,158 women over 57,945.35 person-years. These individuals were HIV negative at baseline. Over the study duration, there were a total of 806 HIV seroconversions in men, and 2,458 HIV seroconversions in women. Our method indicates that establishing a residence outside the rural study area is a strong predictor of HIV seroconversion in men (OR = 2.003, 95% CI = [1.718,2.332]), but not in women. Residing inside the rural study area in a single or in multiple locations is a less significant risk factor for HIV acquisition in both men and women compared to moving outside the rural study area.

A Review on Quinoline Derived Scaffolds as Anti-HIV Agents

After restricting the proliferation of CD4+T cells, Human Immunodeficiency Virus (HIV), infection persists at a very fast rate causing Acquired Immunodeficiency Syndrome (AIDS). This demands the vigorous need of suitable anti-HIV agents, as existing medicines do not provide a complete cure and exhibit drawbacks like toxicities, drug resistance, side-effects, etc. Even the introduction of Highly Active Antiretroviral Therapy (HAART) failed to combat HIV/AIDS completely. The major breakthrough in anti-HIV discovery was marked with the discovery of raltegravir in 2007, the first integrase (IN) inhibitor. Thereafter, the discovery of elvitegravir, a quinolone derivative emerged as the potent HIV-IN inhibitor. Though many more classes of different drugs that act as anti-HIV have been identified, some of which are under clinical trials, but the recent serious focus is still laid on quinoline and its analogues. In this review, we have covered all the quinoline-based derivatives that inhibit various targets and are potential anti-HIV agents in various phases of the drug discovery.

Male Migration, Women Left Behind, and Sexually Transmitted Diseases in Armenia

The effect of male circular labor migration on risks of sexually transmitted diseases (STDs) among women left behind has not been well studied. Our study examines this effect using data from a survey of 1,240 married women in rural Armenia, where international male labor migration has traditionally been very common. A multivariate comparison of women married to migrants and women married to non-migrants finds that the former, ceteris paribus, reported more STD symptoms, on average, and were more likely to report diagnosed STDs than the latter. However, in the case of STD symptoms, this effect is moderated by household income, as the predicted number of STD symptoms reported by migrants’ wives increases as income rises. The findings illustrate the complex tradeoffs that migration entails for left-behind women and are interpreted in the context of the literature on gender, migration, and STDs.

Tracking external introductions of HIV using phylodynamics reveals a major source of infections in rural KwaZulu-Natal, South Africa

Despite increasing access to antiretrovirals, HIV incidence in rural KwaZulu-Natal remains among the highest ever reported in Africa. While many epidemiological factors have been invoked to explain such high incidence, widespread human mobility and viral movement suggest that transmission between communities may be a major source of new infections. High cross-community transmission rates call into question how effective increasing the coverage of antiretroviral therapy locally will be at preventing new infections, especially if many new cases arise from external introductions. To help address this question, we use a phylodynamic model to reconstruct epidemic dynamics and estimate the relative contribution of local transmission versus external introductions to overall incidence in KwaZulu-Natal from HIV-1 phylogenies. By comparing our results with population-based surveillance data, we show that we can reliably estimate incidence from viral phylogenies once viral movement in and out of the local population is accounted for. Our analysis reveals that early epidemic dynamics were largely driven by external introductions. More recently, we estimate that 35 per cent (95% confidence interval: 20-60%) of new infections arise from external introductions. These results highlight the growing need to consider larger-scale regional transmission dynamics when designing and testing prevention strategies.

Migration, Sexual Behavior and the Risk of HIV in Kenya

The association of migration with AIDS in sub-Saharan Africa is well documented, yet the social and behavioral mechanisms underlying this relationship remain poorly understood. Using data from the 1993 Kenya Demographic and Health Survey, this article examines whether migrants are more likely than nonmigrants to have multiple recent sexual partners and not use condoms with those partners. Results indicate that migration is a critical factor in high-risk sexual behavior and that its importance varies by gender and by the direction of movement. Independent of marital and cohabitation status, social milieu, awareness of AIDS, and other crucial influences on sexual behavior, male migrants between urban areas and female migrants within rural areas are much more likely than nonmigrant counterparts to engage in sexual practices conducive to HIV infection. In rural areas, migrants from urban places are more likely than nonmigrants to practice high-risk sex. Given the predominance of men in urban migration and the large volume of circulatory movement between urban and rural areas, these results have serious implications for HIV transmission throughout Kenya.

HIV Prevalence Among Central American Migrants in Transit Through Mexico to the USA, 2009-2013

HIV prevalence was estimated among migrants in transit through Mexico. Data were collected on 9108 Central American migrants during a cross-sectional study performed in seven migrant shelters from 2009 to 2013. Considerations focused on their sociodemographic characteristics, sexual and reproductive health, and experience with violence. Based on a sample of 46.6 % of respondents who agreed to be HIV tested, prevalence of the virus among migrants came to 0.71 %, reflecting the concentrated epidemic in their countries of origin. A descriptive analysis was performed according to gender: the distribution of the epidemic peaked at 3.45 % in the transvestite, transgender and transsexual (TTT) population, but fell to less than 1 % in men and women. This gender differential is characteristic of the epidemic in Central America. Furthermore, 23.5 % of TTTs and 5.8 % of women experienced sexual violence. The predominant impact of sexual violence on TTTs and women will influence the course of the AIDS epidemic.

What Prevents Central Asian Migrant Workers from Accessing HIV Testing? Implications for Increasing HIV Testing Uptake in Kazakhstan

Several barriers prevent key populations, such as migrant workers, from accessing HIV testing. Using data from a cross-sectional study among Central Asian migrant workers (n = 623) in Kazakhstan, we examined factors associated with HIV testing. Overall, 48% of participants had ever received an HIV test. Having temporary registration (AOR 1.69; (95% CI [1.12-2.56]), having an employment contract (AOR 2.59; (95% CI [1.58-4.23]), being able to afford health care services (AOR 3.61; (95% CI [1.86-7.03]) having a medical check-up in the past 12 months (AOR 1.85; 95% CI [1.18-2.89]), and having a regular doctor (AOR 2.37; 95% CI [1.20-4.70]) were associated with having an HIV test. HIV testing uptake among migrants in Kazakhstan falls far short of UNAIDS 90-90-90 goals. Intervention strategies to increase HIV testing among this population may include initiatives that focus on improving outreach to undocumented migrants, making health care services more affordable, and linking migrants to health care.

Phylodynamic applications in 21st century global infectious disease research

BACKGROUND

Phylodynamics, the study of the interaction between epidemiological and pathogen evolutionary processes within and among populations, was originally defined in the context of rapidly evolving viruses and used to characterize transmission dynamics. The concept of phylodynamics has evolved since the early 21st century, extending its reach to slower-evolving pathogens, including bacteria and fungi, and to the identification of influential factors in disease spread and pathogen population dynamics.

RESULTS

The phylodynamic approach has now become a fundamental building block for the development of comparative phylogenetic tools capable of incorporating epidemiological surveillance data with molecular sequences into a single statistical framework. These innovative tools have greatly enhanced scientific investigations of the temporal and geographical origins, evolutionary history, and ecological risk factors associated with the growth and spread of viruses such as human immunodeficiency virus (HIV), Zika, and dengue and bacteria such as Methicillin-resistant Staphylococcus aureus.

CONCLUSIONS

Capitalizing on an extensive review of the literature, we discuss the evolution of the field of infectious disease epidemiology and recent accomplishments, highlighting the advancements in phylodynamics, as well as the challenges and limitations currently facing researchers studying emerging pathogen epidemics across the globe.

Space-time migration patterns and risk of HIV acquisition in rural South Africa

Objective:

To quantify the space-time dimensions of human mobility in relationship to the risk of HIV acquisition.

Methods:

We used data from the population cohort located in a high HIV prevalence, rural population in KwaZulu-Natal, South Africa (2000–2014). We geolocated 8006 migration events (representing 1 028 782 km traveled) for 17 743 individuals (≥15 years of age) who were HIV negative at baseline and followed up these individuals for HIV acquisition (70 395 person-years). Based on the complete geolocated residential history of every individual in this cohort, we constructed two detailed time-varying migration indices. We then used interval-censored Cox proportional hazards models to quantify the relationship between the migration indices and the risk of HIV acquisition.

Results:

In total, 17.4% of participants migrated at least once outside the rural study community during the period of observation (median migration distance = 107.1 km, interquartile range 18.9–387.5). The two migration indices were highly predictive of hazard of HIV acquisition (P < 0.01) in both men and women. Holding other factors equal, the risk of acquiring HIV infection increased by 50% for migration distances of 40 km (men) and 109 km (women). HIV acquisition risk also increased by 50% when participants spent 44% (men) and 90% (women) of their respective time outside the rural study community.

Conclusion:

This in-depth analysis of a population cohort in a rural sub-Saharan African population has revealed a clear nonlinear relationship between distance migrated and HIV acquisition. Our findings show that even relatively short-distance migration events confer substantial additional risk of acquisition.

HIV Infection Among Transport Workers Operating Through Siliguri-Guwahati National Highway, India

A community-based cross-sectional study was conducted in July 2004 to understand the problem of HIV and other sexually transmitted infections among long-distance transport workers operating through the Siliguri-Guwahati national highway. The study included 301 transport workers who were contacted at different transport workers’ stops on the Siliguri-Guwahati national highway. Informed consent was obtained. Participants were interviewed for their socio-demographic characteristics, risk behavior, and risk perceptions. Blood testing for HIV, hepatitis B virus, and syphilis (at least 1:8 dilution) showed seroprevalence rates of 2.3%, 3.7%, and 6.3%, respectively. About 67% said they visited sex workers. The reported condom use rate was 58%. About 27% sustained a sexually transmitted infection within the last year. The existing HIV prevalence among transport workers appears to be low, but in view of their risk behavior and high rate of sexually transmitted infection, HIV rates may increase unless a suitable behavioral intervention is urgently initiated toward them.

'Deadly gonorrhoea': history, collective memory and early HIV epidemiology in East Central Africa

This article combines local oral reminiscences with recent epidemiological literature to sketch a historical context around the onset and expansion of the HIV-1 epidemic in southern Uganda and north-western Tanzania. The local historical imagination has associated the appearance of AIDS in two ways. First, with specific socio-economic structures and circumstances common in the region since the 1960s and their enhancement during the 1970s due to economic changes at national and global levels. Second, the epidemic is associated with changes in the epidemiological situation. Local perspectives are supported by recent phylogenetic research and circumstantial historical evidence, on the basis of which a hypothesis on the expansion of HIV-1 in East Central Africa (southern Uganda, north-western Tanzania, Rwanda) is presented.

Per capita incidence of sexually transmitted infections increases systematically with urban population size: a cross-sectional study

OBJECTIVES

Rampant urbanisation rates across the globe demand that we improve our understanding of how infectious diseases spread in modern urban landscapes, where larger and more connected host populations enhance the thriving capacity of certain pathogens.

METHODS

A data-driven approach is employed to study the ability of sexually transmitted diseases (STDs) to thrive in urban areas. The conduciveness of population size of urban areas and their socioeconomic characteristics are used as predictors of disease incidence, using confirmed-case data on STDs in the USA as a case study.

RESULTS

A superlinear relation between STD incidence and urban population size is found, even after controlling for various socioeconomic aspects, suggesting that doubling the population size of a city results in an expected increase in STD incidence larger than twofold, provided that all other socioeconomic aspects remain fixed. Additionally, the percentage of African-Americans, income inequalities, education and per capita income are found to have a significant impact on the incidence of each of the three STDs studied.

CONCLUSIONS

STDs disproportionately concentrate in larger cities. Hence, larger urban areas merit extra prevention and treatment efforts, especially in low-income and middle-income countries where urbanisation rates are higher.

Migrant workers in Sabah, East Malaysia: The importance of legislation and policy to uphold equity on sexual and reproductive health and rights

Sabah, located in Southeast Asia, hosts the highest number of non-Malaysian citizens (27.7%), predominantly the Indonesian and Filipino migrants in comparison to other states in Malaysia. Sabah has inadequate data on migrants' sexual and reproductive health and rights (SRHRs). Various migrant-related policies and laws are present, but they do not offer full protection and rights to legal migrants in terms of their SRHRs. The aim of the laws and policies appears to be controlling the migrants from having any negative impact on the locals, rather than protecting migrants' health and rights. This affected their rights to marriage, having children, increase their vulnerabilities to labour trafficking and sexual abuse and access to health-care services. Female migrant workers and undocumented migrants form the most vulnerable subgroups of migrants. This narrative review highlights the status of SRHRs of migrants in Sabah and the migrant-related Malaysian laws and policies affecting their SRHRs.

Mobility among youth in Rakai, Uganda: Trends, characteristics, and associations with behavioural risk factors for HIV

Mobility, including migration and travel, influences risk of HIV. This study examined time trends and characteristics among mobile youth (15-24 years) in rural Uganda, and the relationship between mobility and risk factors for HIV. We used data from an annual household census and population-based cohort study in the Rakai district, Uganda. Data on in-migration and out-migration were collected among youth (15-24 years) from 43 communities from 1999 to 2011 (N = 112,117 observations) and travel among youth residents from 2003 to 2008 (N = 18,318 observations). Migration and travel were more common among young women than young men. One in five youth reported out-migration. Over time, out-migration increased among youth and in-migration remained largely stable. Primary reasons for migration included work, living with friends or family, and marriage. Recent travel within Uganda was common and increased slightly over time in teen women (15-19 years old), and young adult men and women (20-24 years old). Mobile youth were more likely to report HIV-risk behaviours including: alcohol use, sexual experience, multiple partners, and inconsistent condom use. Our findings suggest that among rural Ugandan youth, mobility is increasingly common and associated with HIV-risk factors. Knowledge of patterns and characteristics of a young, high-risk mobile population has important implications for HIV interventions.

Conceptual framework and research methods for migration and HIV transmission dynamics

Migration and mobility have had a profound influence on the global HIV epidemic. We propose a network-dyadic conceptual model to interpret previous literature and inform the development of future research with respect to study design, measurement methods, and analytic approach. In this model, HIV transmission is driven by risk behaviors of migrants that emerges and is enabled by mobility, the bridging of sub-epidemics across space and time, and the displacement effects on the primary residential sending community for migrants. To investigate these causal pathways, empirical study designs must measure the relative timing of migratory events, sexual risk behaviors, and incident HIV infections. Network-based mathematical models using empirical data on partnerships help gain insight into the dynamic disease transmission systems. Although the network-dyadic conceptual model and related network methods may not address all questions related to migration and HIV, they provide a unified approach for future research on this important topic.

HIV epidemiology. The early spread and epidemic ignition of HIV-1 in human populations

Thirty years after the discovery of HIV-1, the early transmission, dissemination, and establishment of the virus in human populations remain unclear. Using statistical approaches applied to HIV-1 sequence data from central Africa, we show that from the 1920s Kinshasa (in what is now the Democratic Republic of Congo) was the focus of early transmission and the source of pre-1960 pandemic viruses elsewhere. Location and dating estimates were validated using the earliest HIV-1 archival sample, also from Kinshasa. The epidemic histories of HIV-1 group M and nonpandemic group O were similar until ~1960, after which group M underwent an epidemiological transition and outpaced regional population growth. Our results reconstruct the early dynamics of HIV-1 and emphasize the role of social changes and transport networks in the establishment of this virus in human populations.

HIV epidemiology. The early spread and epidemic ignition of HIV-1 in human populations

Thirty years after the discovery of HIV-1, the early transmission, dissemination, and establishment of the virus in human populations remain unclear. Using statistical approaches applied to HIV-1 sequence data from central Africa, we show that from the 1920s Kinshasa (in what is now the Democratic Republic of Congo) was the focus of early transmission and the source of pre-1960 pandemic viruses elsewhere. Location and dating estimates were validated using the earliest HIV-1 archival sample, also from Kinshasa. The epidemic histories of HIV-1 group M and nonpandemic group O were similar until ~1960, after which group M underwent an epidemiological transition and outpaced regional population growth. Our results reconstruct the early dynamics of HIV-1 and emphasize the role of social changes and transport networks in the establishment of this virus in human populations.

What can mathematical models tell us about the relationship between circular migrations and HIV transmission dynamics?

Circular migrations are the periodic movement of individuals between multiple locations, observed in parts of sub-Saharan Africa. Relationships between circular migrations and HIV are complex, entailing interactions between migration frequency, partnership structure, and exposure to acute HIV infection. Mathematical modeling is a useful tool for understanding these interactions. Two modeling classes have dominated the HIV epidemiology and policy literature for the last decade: one a form of compartmental models, the other network models. We construct models from each class, using ordinary differential equations and exponential random graph models, respectively. Our analysis suggests that projected HIV prevalence is highly sensitive to the choice of modeling framework. Assuming initial equal HIV prevalence across locations, compartmental models show no association between migration frequency and HIV prevalence or incidence, while network models show that migrations at frequencies shorter than the acute HIV period predict greater HIV incidence and prevalence compared to longer migration periods. These differences are statistically significant when network models are extended to incorporate a requirement for migrant men's multiple partnerships to occur in different locations. In settings with circular migrations, commonly-used forms of compartmental models appear to miss key components of HIV epidemiology stemming from interactions of relational and viral dynamics.

Migration intensity has no effect on peak HIV prevalence: an ecological study

Background

Correctly identifying the determinants of generalized HIV epidemics is crucial to bringing down ongoing high HIV incidence in these countries. High rates of migration are believed to be an important determinant of HIV prevalence. This study has two aims. Firstly, it evaluates the ecological association between levels of internal and international migration and national peak HIV prevalence using thirteen variables from a variety of sources to capture various aspects of internal and international migration intensity. Secondly, it examines the relationship between circular migration and HIV at an individual and population-level in South Africa.

Methods

Linear regression was used to analyze the association between the various measures of migration intensity and peak national HIV prevalence for 141 countries and HIV prevalence by province and ethnic group in South Africa.

Results

No evidence of a positive ecological association between national migration intensity and HIV prevalence was found. This remained the case when the analyses were limited to the countries of sub-Saharan Africa. On the whole, countries with generalized HIV epidemics had lower rates of internal and external migration. Likewise, no association was found between migration and HIV positivity at an individual or group-level in South Africa.

Conclusion

These results do not support the thesis that migration measured at the country level plays a significant role in determining peak HIV prevalence.

Ubiquitous burden: the contribution of migration to AIDS and Tuberculosis mortality in rural South Africa

The paper aims to estimate the extent to which migrants are contributing to AIDS or tuberculosis (TB) mortality among rural sub-district populations. The Agincourt (South Africa) health and socio-demographic surveillance system provided comprehensive data on vital and migration events between 1994 and 2006. AIDS and TB cause-deleted life expectancy, and crude death rates by gender, migration status and period were computed. The annualised crude death rate almost tripled from 5·39 [95% CI 5·13-5·65] to 15·10 [95% CI 14·62-15·59] per 1000 over the years 1994-2006. The contribution of AIDS and TB in returned migrants to the increase in crude death rate was 78·7% [95% CI 77·4-80·1] for males and 44·4% [95% CI 43·2-46·1] for females. So, in a typical South African setting dependent on labour migration for rural livelihoods, the contribution of returned migrants, many infected with AIDS and TB, to the burden of disease is high.

Migration and Health in Southern Africa: 100 years and still circulating

Migration has deep historical roots in South and Southern Africa and to this day continues to be highly prevalent and a major factor shaping South African society and health. In this paper we examine the role of migration in the spread of two diseases nearly 100 years apart: tuberculosis following the discovery of gold in 1886 and HIV in the early 1990s. Both cases demonstrate the critical role played by human migration in the transmission and subsequent dissemination of these diseases to rural areas. In both cases, migration acts to assemble in one high-risk environment thousands of young men highly susceptible to new diseases. With poor living and working conditions, these migration destinations act as hot-spots for disease transmission. Migration of workers back to rural areas then serves as a highly efficient means of disseminating these diseases to rural populations. We conclude by raising some more recent questions examining the current role of migration in Southern Africa.

Strong association between in-migration and HIV prevalence in urban sub-Saharan Africa

BACKGROUND

Enormous variation exists in HIV prevalence between countries in sub-Saharan Africa. The contribution of migration to the spread of HIV has long been recognized, but its effect at the population level has never been assessed. In this ecological analysis, we explore how much variation in HIV prevalence in urban sub-Saharan Africa is explained by in-migration.

METHODS

We performed a linear regression to analyze the association between the proportion of recent in-migrants and HIV prevalence for men and women in urban areas, using 60 data points from 28 sub-Saharan African countries between 1987 and 2005.

RESULTS

We found a strong association between recent in-migration and HIV prevalence for women (Pearson R = 57%, P < 0.001) and men (R = 24%, P = 0.016), taking the earliest data point for each country. For women, the association was also strong within east/southern Africa (R = 50%, P = 0.003). For both genders, the association was strongest between 1985 and 1994, slightly weaker between 1995 and 1999, and nonexistent as from 2000. The overall association for both men and women was not confounded by the developmental indicators GNI per capita, income inequalities, or adult literacy.

CONCLUSIONS

Migration explains much of the variation in HIV spread in urban areas of sub-Saharan Africa, especially before the year 2000, after which HIV prevalences started to level off in many countries. Our findings suggest that migration is an important factor in the spread of HIV, especially in rapidly increasing epidemics. This may be of relevance to the current HIV epidemics in China and India.

High level of HIV-2 false positivity in KwaZulu-Natal province: a region of South Africa with a very high HIV-1 subtype C prevalence

Human immunodeficiency virus 2 (HIV-2) is found predominantly in West Africa. It is not unlikely, however, that HIV-2 may also be found in South Africa, due to the influx of immigrants into this country. It is important to distinguish between HIV-1 and HIV-2 since the clinical courses and treatment responses of these viruses are different. Routine serological methods for diagnosing HIV do not differentiate between HIV-1 and -2 infections, while rapid tests, viral load quantification and PCR are HIV-type--specific. The objective of this study was to describe the seroprevalence and molecular epidemiology of HIV-2 in KwaZulu-Natal, one of the regions with the highest HIV prevalence in the world and home of the two largest harbors in South Africa. HIV-1 positive samples were screened for antibodies against HIV-2, using a rapid test. The confirmation of HIV-2 positive samples was done by PCR. Of the 2,123 samples screened, 319 (15%) were identified as positive by the rapid test. None of these samples were confirmed positive by PCR. To explore this discrepancy in the results, a subset (n = 52) of the rapid HIV-2 positive samples was subjected to Western blotting. Thirty-seven (71%) of these were positive, yielding an overall HIV-2 seroprevalence of 10.6%. Three out of 28 (10.7%) Western blot positive samples were positive by a Pepti-LAV assay. This discrepancy between serological and molecular confirmation may be attributed to non-specific or cross-reacting antibodies. The use of rapid tests and Western blots for HIV-2 diagnosis in South Africa should be interpreted with caution.

Short-term Mobility and Increased Partnership Concurrency among Men in Zimbabwe

BACKGROUND

Migration has long been understood as an underlying factor for HIV transmission, and sexual partner concurrency has been increasingly studied as an important component of HIV transmission dynamics. However, less work has examined the role of short-term mobility in sexual partner concurrency using a network approach. Short-term mobility may be a risk for HIV for the migrant's partner as well either through the partner's risk behaviors while the migrant is away, such as the partner having additional partners, or via exposure to the return migrant.

METHODS

Using data from the 2010-11 Zimbabwe Demographic and Health Survey, weighted generalized linear regression models were used to investigate the associations between short-term mobility and partnership concurrency at the individual and partnership levels.

RESULTS

At the individual level, we find strong evidence of an association between short-term mobility and concurrency. Men who traveled were more likely to have concurrent partnerships compared to men who did not travel and the relationship was non-linear: each trip was associated with a 2% higher probability of concurrency, with a diminishing risk at 60 trips (p<0.001). At the partnership level, short-term mobility by the male only or both partners was associated with male concurrency. Couples in which the female only traveled exhibited less male concurrency.

CONCLUSIONS

Short-term mobility has the ability to impact population-level transmission dynamics by facilitating partnership concurrency and thus onward HIV transmission. Short-term migrants may be an important population to target for HIV testing, treatment, or social and behavioral interventions to prevent the spread of HIV.

Comparing HIV-1 and HIV-2 infection: Lessons for viral immunopathogenesis

HIV-1 and HIV-2 share many similarities including their basic gene arrangement, modes of transmission, intracellular replication pathways and clinical consequences: both result in AIDS. However, HIV-2 is characterised by lower transmissibility and reduced likelihood of progression to AIDS. The underlying mechanistic differences between these two infections illuminate broader issues of retroviral pathogenesis, which remain incompletely understood. Comparisons between these two infections from epidemiological, clinical, virologic and immunologic viewpoints provide a basis for hypothesis generation and testing in this 'natural experiment' in viral pathogenesis. In terms of epidemiology, HIV-2 remains largely confined to West Africa, whereas HIV-1 extends worldwide. Clinically, HIV-2 infected individuals seem to dichotomise, most remaining long-term non-progressors, whereas most HIV-1 infected individuals progress. When clinical progression occurs, both diseases demonstrate very similar pathological processes, although progression in HIV-2 occurs at higher CD4 counts. Plasma viral loads are consistently lower in HIV-2, as are average levels of immune activation. Significant differences exist between the two infections in all components of the immune system. For example, cellular responses to HIV-2 tend to be more polyfunctional and produce more IL-2; humoral responses appear broader with lower magnitude intratype neutralisation responses; innate responses appear more robust, possibly through differential effects of tripartite motif protein isoform 5 alpha. Overall, the immune response to HIV-2 appears more protective against disease progression suggesting that pivotal immune factors limit viral pathology. If such immune responses could be replicated or induced in HIV-1 infected patients, they might extend survival and reduce requirements for antiretroviral therapy.

HIV/AIDS surveillance data for New York City West Indian-born Blacks: comparisons with other immigrant and US-born groups

OBJECTIVES

Although the risk of HIV among New York City West Indian-born Black immigrants often is assumed to be high, population-based data are lacking, a gap we aimed to address.

METHODS

Using 2006-2007 HIV/AIDS surveillance data from the New York City Department of Health and Mental Hygiene and population data from the US Census American Community Survey 2007, we compared the rate of newly reported HIV diagnoses, prevalence of people living with HIV/AIDS, and distribution of transmission risk categories in West Indian-born Blacks, 2 other immigrant groups, and US-born Blacks and Whites.

RESULTS

The age-adjusted rate of newly reported HIV diagnoses for West Indian-born Blacks was 43.19 per 100 000 (95% confidence interval [CI] = 38.92, 49.10). This was higher than the rate among US-born Whites (19.96; 95% CI = 18.63, 21.37) and Dominican immigrants and lower than that among US-born Blacks (109.48; 95% CI = 105.02, 114.10) and Haitian immigrants. Heterosexual transmission was the largest risk category in West Indian-born Blacks, accounting for 41% of new diagnoses.

CONCLUSIONS

Although much lower than in US-born Blacks, the rate of newly reported HIV diagnoses in West Indian-born Blacks exceeds that among US-born Whites. Additional work is needed to understand the migration-related sources of risk.

Understanding out-migration among female sex workers in South India

BACKGROUND

Migrant sex workers are known to be vulnerable to HIV. There is substantial female sex worker (FSW) mobility between the borders of Maharashtra and Karnataka, but little programming emphasis on migrant FSWs in India. We sought to understand the individual/cultural, structural, and contextual determinants of migration among FSWs from Karnataka.

METHODS

A cross-sectional face-to-face interview of 1567 FSWs from 142 villages in 3 districts of northern Karnataka, India was conducted from January to June 2008. Villages having 10+ FSWs, a large number of whom were migrant, were selected following mapping of FSWs. Multinomial logistic regression was conducted to identify characteristics associated with migrant (travelled for ≥ 2 weeks outside the district past year) and mobile (travelled for <2 weeks outside the district past year) FSWs; adjusting for age and district.

RESULTS

Compared with nonmigrants, migrant FSWs were more likely to be brothel than street based (Adjusted Odds Ratio (AOR): 5.7; 95% confidence interval: 1.6-20.0), have higher income from sex work (Adjusted Odds Ratio (AOR): 42.2; 12.6-142.1), speak >2 languages (AOR: 5.6; 2.6-12.0), have more clients (AOR per client: 2.9; 1.2-7.2), and have more sex acts per day (AOR per sex act: 3.5; 1.3-9.3). Mobile FSWs had higher income from sex work (AOR: 13.2; 3.9-44.6) relative to nonmigrants, but not as strongly as for migrant FSWs.

CONCLUSION

Out-migration of FSWs in Karnataka was strongly tied to sex work characteristics; thus, the structure inherent in sex work should be capitalized on when developing HIV preventive interventions. The important role of FSWs in HIV epidemics, coupled with the potential for rapid spread of HIV with migration, requires the most effective interventions possible for mobile and migrant FSWs.

Male migration/mobility and HIV among married couples: cross-sectional analysis of nationally representative data from India

This paper examines the associations between male migration and mobility with HIV among married couples in India. Cross-sectional analyses of a nationally representative household survey conducted across all 29 states of India from 2005 to 2006 via the National Family Health Survey-3 (NFHS-3) included a subsample of 27,771 married couples who were tested for HIV as a part of their participation. Both bi-variate and multi-variate analyses were conducted. About 0.5% of the total married couples in the current study included an HIV-infected partner; 0.11% were HIV concordant and 0.38% were HIV serodiscordant couples. Adjusted logistic regression analyses demonstrated that HIV infection in couples (seroconcordant or serodiscordant) was significantly more likely among those couples where the man was migrant but not mobile and those couples where the man was migrant as well as mobile, relative to those couples where the man was neither migrant nor mobile. Male migration increases the risk for HIV among married couples in India, largely in the form of serodiscordance in which men are HIV infected. These findings document the need for not only primary prevention efforts to reduce HIV acquisition among migrant male workers, particularly more mobile migrants, but also efforts are needed to reduce subsequent transmission to their wives.

Urbanization and Infectious Diseases: General Principles, Historical Perspectives, and Contemporary Challenges

In 2009, a major demographic line was crossed: for the first time in history, the majority of the world population lived in cities rather than in towns and countryside (Fig. 4.1). This shift has been occurring over the past 100 years, with the most rapid rate of urban growth occurring over in the latter half of the twentieth century. Urban centers in the more developed regions of the world (i.e., North America, Australia, New Zealand, and Europe) experienced earlier growth in the 1920s–1950s, and since then, the rapid rate of urban growth has been concentrated in the cities and towns of developing nations [1].

"I am tired but if I don't try to have sex, my wife will think I've been fooling around in the city": work, migration, and sex among Vietnamese migrant laborers

Mostly operating from a risk and risk-reduction paradigm, existing research on migrants in Vietnam tends to conceptualize sex and risky sexual behaviors as isolated life domains. This study begins to develop a contextually rich understanding of migrants' sex lives by examining the relationships among sex, work, and the constant pendulum-like migrating movements of 23 Vietnamese married migrants in Hanoi and Ho Chi Minh City. Using data from in-depth interviews, it was found that most participants had no sex in the city; this was followed by visits to the home village, where they had sex with their spouses as often as possible to make up for the "long drought" in the city. Within this sexual schema, sex came secondary, and even peripherally, to migrants' working lives; thus, exhaustion from work was cited by migrants as the overwhelming factor leading to their sexual problems. This study suggests that migrants' intimate lives are more strongly linked to their working lives than has previously been recognized, and that their sexual behaviors should be viewed in tandem with the hardships of their working lives.

[HIV/AIDS care and international migrations in the rural district of Nanoro, Burkina Faso]

West African Countries account for almost half of the estimated 20 000 000 international migrants in the continent. In the frame of the scaling up of HAART, our study aims to identify specific features and constraints of access to care for HIV migrant patients returning to Burkina Faso. From January 2007 to August 2011, the Nanoro District Hospital, serving a rural area in the Centre-West of Burkina Faso, followed 437 HIV/AIDS adult patients. Migrants were 139/437 (31.8 %), of whom 108/139 (77.7 %), declared they returned to Burkina Faso to seek care, because the area they migrated to did not offer specific HIV health assistance. At baseline, 113/139 (81,3 %) migrants and 181/298 (60,7 %) residents were in WHO clinical stages III or IV (p< 0.01). For every 100 patients/ year under HAART, 25.5 migrants (91.4 % of whom to foreign countries) and 5.7 Burkina residents were transferred to other centers (p<0.01). 21.8 migrants and 8.5 residents were dead or lost to follow up (p<0.05). For migrant patients, access to HIV screening and care seems to be delayed. The high frequency of migrants under HAART working abroad requires an improved cooperation among the health systems of the African Countries.

Phylodynamics of the HIV-1 CRF02_AG clade in Cameroon

Evolutionary analyses have revealed an origin of pandemic HIV-1 group M in the Congo River basin in the first part of the XX century, but the patterns of historical viral spread in or around its epicentre remain largely unexplored. Here, we combine epidemiologic and molecular sequence data to investigate the spatiotemporal patterns of the CRF02_AG clade. By explicitly integrating prevalence counts and genetic population size estimates we date the epidemic emergence of CRF02_AG at 1973.1 (1972.1, 1975.3, 95% CI). To infer the phylogeographic signature of this clade at a regional scale, we analyze pol and env time-stamped sequence data from 10 countries using a Bayesian phylogeographic approach based on an asymmetric discretized diffusion model. Our data confirms a spatial origin of CRF02_AG in the Democratic Republic of Congo (DRC) and suggests that viral dissemination to Cameroon occurred at an early stage of the evolutionary history of CRF02_AG. We find considerable support for epidemiological linkage between neighbour countries. Compilation of ethnographic data suggested that well-supported viral migration did not reflect sustained human migratory flows. Finally, using sequence data from 15 locations in Cameroon, we use relaxed random walk models to explore the spatiotemporal dynamics of CRF02_AG at a finer geographical detail. Phylogeographic dispersal in continuous space reveals that at least two distinct CRF02_AG lineages are circulating in overlapping regions that are evolving at different evolutionary and diffusion rates. In conclusion, by combining molecular and epidemiological data, our results provide a time scale for CRF02_AG, early 70s, place its spatial root in the DRC within the putative root of group-M diversity and propose a scenario of chance-exportation events for the spatiotemporal patterns of a successful HIV-1 lineage both at a regional and country-scale.

Impact of HIV/AIDS on Social Relationships in Rural China

Social support promotes greater medical compliance, better immune system functioning and slows the progress of HIV/AIDS. One in every 50 People Living With HIV/AIDS (PLWHA) is Chinese, yet little is known about the impact of HIV/AIDS on social relationships in China. This study compares the characteristics of those who report that HIV/AIDS had a substantial impact versus a modest impact on their social relationships. We obtained data from a survey of 866 PLWHA in rural China, which was conducted in 2006-2007 in the three Chinese provinces with the highest prevalence of HIV/AIDS. Chi-square test and multiple logistic regression were performed. The analysis shows that PLWHA who had full-blown AIDS (OR= 1.53; 95% CI=1.09-2.13) and those who were poor (OR=2.19; 95% CI=1.52-3.16) reported greater impact on their social relationships. The results lay a solid foundation for designing effective policy initiatives and intervention programs aimed at alleviating the impact of HIV/AIDS on social relationships and improving the quality of life of PLWHA.

Health Costs of Wealth Gains: Labor Migration and Perceptions of HIV/AIDS Risks in Mozambique

The study employs survey data from rural Mozambique to examine how men's labor migration affects their non-migrating wives' perceptions of HIV/AIDS risks. Using a conceptual framework centered on tradeoffs between economic security and health risks that men's migration entails for their left-behind wives, it compares women married to migrants and those married to non-migrants while also distinguishing between economically successful and unsuccessful migration. The analysis finds that the economic success of men's migration, rather than migration itself, significantly predicts women's worries about getting infected by their husbands or their own extramarital partners, and their husbands' stance on condom use. These findings are situated within a broader context of socio-economic, gender, and marital dynamics and vulnerabilities produced or amplified by male labor migration in sub-Saharan and similar developing settings.

HIV care for geographically mobile populations

The interaction between geographic mobility and risk for human immunodeficiency virus infection is well recognized, but what happens to those same individuals, once infected, as they transition to living with the infection? Does mobility affect their transition into medical care? If so, do mobile and nonmobile populations achieve similar success with antiretroviral treatment? The definition of mobility has changed over the centuries to encompass a complex phenotype including permanent migration, frequent travel, circular migration, and travel to and from treatment centers. The heterogeneity of these definitions leads to discordant findings. Investigations show that mobility has an impact on infection risk, but fewer data exist on the impact of geographic mobility on medical care and treatment outcomes. This review will examine existing data regarding the impact of geographic mobility on access to and maintenance in medical care and on adherence to antiretroviral therapy for those living with human immunodeficiency virus infection. It will also expand the concept of mobility to include data on the impact of the distance from residence to clinic on medical care and treatment adherence. Our conclusions are that the existing literature is limited by varying definitions of mobility and the inherent oversimplification necessary to apply a "mobility measure" in a statistical analysis. The impact of mobility on antiretroviral treatment outcomes deserves further exploration to both define the phenomenon and target interventions to these at-risk populations.

Contexts of risk and networks of protection: NYC West Indian immigrants' perceptions of migration and vulnerability to sexually transmitted diseases

To generate insights into how migration shapes sexual risk and protection, we interviewed 36 female and 20 male West Indian immigrants attending a public sexually transmitted disease clinic in Brooklyn, New York, between 2004 and 2005. Migration theory suggests that shifts in sexual partnership patterns, bi-directional travel and changes in sexual norms may alter risk. We found evidence of sexual mixing across ethnic groups: a large proportion of participants' partners were not born in the West Indies, despite what is expected among first generation immigrants. Recent travel 'home', another potential source of risk, was uncommon. In open-ended interviews, two themes around sexual and social networks emerged. First, immigrants believed that access to wider, more anonymous sexual networks in New York City (NYC) and the weakening of social controls that limit multiple partnerships (especially for women) promoted greater risk. Second, immigrants experienced greater opportunities for protection in NYC, both through exposure to safer sex messages and availability of condoms. Reported changes in their own condom use, however, were not attributed to migration. West Indian immigrants' risk in NYC may be driven by access to wider sexual networks but failure to alter reliance on 'networks of knowledge' for protection.

The impact of mobility on HIV control: a modelling study

Mobility is associated with HIV due to more risky sexual behaviour of mobile groups such as travellers and migrants. Limited participation of such groups may reduce the effectiveness of HIV interventions disproportionally. The established STDSIM model, which simulates transmission and control of HIV and STD, was extended to simulate mobility patterns based on data from Tanzania. We explored the impact of non-participation of mobile groups (travellers and recent migrants) on the effectiveness of two interventions: condom promotion and health education aiming at partner reduction. If mobile groups do not participate, the effectiveness of both interventions could be reduced by 40%. The impact of targeting travellers with a combined HIV campaign is close to that of a general population intervention. In conclusion, it is important to account for possible non-participation of migrants and travellers. If non-participation is substantial, impact of interventions can be greatly improved by actively approaching these people.

Linking migration, mobility and HIV

Population mobility is commonly identified as a key driver of the HIV epidemic, both linking geographically separate epidemics and intensifying transmission through inducing riskier sexual behaviours. However, beyond the well-known case studies of South African miners and East African truck drivers, the evidence on the links between HIV and mobility is nuanced, contradictory and inconclusive and is in part attributed to the abstract definitions of mobility used in different studies. This problematic conception of mobility, with no reference to who moves, their motivations for moving, or the characteristics of sending and receiving areas, can have a dramatic impact on how one understands the influence which this structural factor has on HIV risk in different settings. Future research on mobility and HIV transmission must incorporate an understanding of migration and mobility as dynamic processes and link different patterns and forms of mobility with location-specific sexual networks and HIV epidemiology.

Disassortative sexual mixing among migrant populations in The Netherlands: a potential for HIV/STI transmission?

To gain insight into the transmission of HIV and sexually transmitted infection (STI) among large migrant groups in The Netherlands, we studied the associations between their demographic and sexual characteristics, in particular condom use, and their sexual mixing patterns with other ethnic groups. In 2002-2005, cross-sectional surveys were conducted among migrants from Surinam (Afro- and Hindo-), the Netherlands Antilles, Cape Verde, and Ghana at social venues in three large cities. A questionnaire was administrated and a saliva sample was collected for HIV antibody testing. Of 2105 migrants recruited, 1680 reported sexual contacts, of whom 41% mixed sexually with other ethnicities, including the indigenous Dutch population. Such disassortative mixing was associated with being second-generation migrant, having several sexual partners, and having a steady and concurrent casual partner. Less disassortative mixing occurred in participants reporting visiting the country of origin. The association between condom use and sexual mixing differed by gender, with men using condoms inconsistently being most likely to be mixing with the Dutch indigenous population. HIV infection and recent STI treatment were not associated with disassortative mixing. This study shows substantial sexual mixing among migrant groups. Since disassortative mixing is more prevalent in second-generation migrants, it might increase in the upcoming years. The mixing patterns in relation to concurrency and the reported condom use in this study suggest a possibly increased level of HIV/STI transmission not only within migrant groups but also between migrant groups, especially via men who mix with the indigenous population and via migrant women who mix with non-Dutch casual partners. Although the observed HIV prevalence in migrants (0.6%) is probably too low to lead to much HIV transmission between ethnicity groups, targeted prevention measures are needed to prevent transmission of other STI.

Dual HIV Infection Uncommon in Patients on Antiretroviral Therapy in a Region with High HIV Prevalence

Dual HIV infection has been found in regions with high HIV prevalence and in populations infected with diverse strains of HIV. The prevalence of dual infection in KwaZulu-Natal (KZN), where there is a high prevalence of HIV and an influx of immigrants who may be infected with different HIV subtypes, is unknown. The aim of this study was to determine the prevalence of dual infection in KZN. Eighty-three samples were obtained from chronically infected patients on ARV treatment from sites throughout KZN. Subtyping of the samples was performed using the heteroduplex mobility assay (HMA). Twelve samples that had possible dual infection by HMA were cloned and sequenced. Phylogenetic analysis showed that there was no dual infection in these samples. Contrary to a previous study, we did not find dual infection in this region. The patients in our study may be different from those in the previous study in terms of transmission risk factors, treatment, and stage of infection (acute vs. chronic). This study may have important implications for vaccine development and for the pathogenesis and treatment of dual HIV infection.

Unappreciated epidemiology: the churn effect in a regional HIV care programme

High levels of geographic mobility in and out of HIV care centres (i.e. the churn effect) can disrupt the continuity of patient care, misalign prevention services, impact local prevalence data perturbing optimal allocation of resources, and contribute to logical challenges in repeated transfer of health records. We report on the clinical, demographic, and administrative impact of high population turnover within HIV populations.