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Concept: Sexual network


Assortative mixing in networks is the tendency for nodes with the same attributes, or metadata, to link to each other. It is a property often found in social networks, manifesting as a higher tendency of links occurring between people of the same age, race, or political belief. Quantifying the level of assortativity or disassortativity (the preference of linking to nodes with different attributes) can shed light on the organization of complex networks. It is common practice to measure the level of assortativity according to the assortativity coefficient, or modularity in the case of categorical metadata. This global value is the average level of assortativity across the network and may not be a representative statistic when mixing patterns are heterogeneous. For example, a social network spanning the globe may exhibit local differences in mixing patterns as a consequence of differences in cultural norms. Here, we introduce an approach to localize this global measure so that we can describe the assortativity, across multiple scales, at the node level. Consequently, we are able to capture and qualitatively evaluate the distribution of mixing patterns in the network. We find that, for many real-world networks, the distribution of assortativity is skewed, overdispersed, and multimodal. Our method provides a clearer lens through which we can more closely examine mixing patterns in networks.

Concepts: Sociology, Networks, Social network, Sexual network, Network theory, Network science, Complex network, Social networks


To explore whether gender differences in sexual risk and sexually transmitted infections (STIs) among homeless youth may be explained in part by gender differences in their social networks.

Concepts: Sexually transmitted disease, Human sexual behavior, Sexual network


Sexually transmitted infections (STIs) comprise a significant portion of the infectious-disease burden among rural people in the Global South. Particular characteristics of ruralness-low-density settlements and poor infrastructure-make healthcare provision difficult, and remoteness, typically a characteristic of ruralness, often compounds the difficultly. Remoteness may also accelerate STI transmission, particularly that of viral STIs, through formation of small, highly connected sexual networks through which pathogens can spread rapidly, especially when partner concurrency is broadly accepted. Herein, we explored the effect of remoteness on herpes simplex virus type-2 (HSV-2) epidemiology among semi-nomadic pastoralists in northwestern (Kaokoveld) Namibia, where, in 2009 we collected HSV-2-specific antibody status, demographic, sexual network, and travel data from 446 subjects (women = 213, men = 233) in a cross-sectional study design. HSV-2 prevalence was high overall in Kaokoveld (>35%), but was heterogeneously distributed across locally defined residential regions: some regions had significantly higher HSV-2 prevalence (39-48%) than others (21-33%). Using log-linear models, we asked the following questions: 1) Are sexual contacts among people in high HSV-2-prevalence regions more likely to be homophilous (i.e., from the same region) than those among people from low-prevalence regions? 2) Are high-prevalence regions more “functionally” remote, in that people from those regions are more likely to travel within their own region than outside, compared to people from other regions? We found that high-prevalence regions were more sexually homophilous than low-prevalence regions and that those regions also had higher rates of within-region travel than the other regions. These findings indicate that remoteness can create contact structures for accelerated STI transmission among people who are already disproportionately vulnerable to consequences of untreated STIs.

Concepts: AIDS, Epidemiology, Herpes simplex, Sexually transmitted disease, Human sexual behavior, Sexually transmitted diseases and infections, Sexual network


In today’s media environment, information is not simply passed from producers to consumers, but is mediated by participants of new media cultures, including information on sexual health. In focus groups held in Sydney and regional Australia in 2011, we asked young people aged 16-22 about the potential for sexual health promotion via Facebook and other social media. Our findings point to the complex ways in which young people use social media, and the unlikelihood of traditional take-home sexual health messages having traction in social media spaces. Five key aspects which emerged were: the participatory culture of social network sites; the stigma of sexual health, especially sexually transmitted infections (STIs); young people’s careful presentations of self; privacy concerns; and the importance of humour in sexual health messaging. Fears of bullying and gossip (or ‘drama’) were also likely to prevent the dissemination of sexual health messages in this environment. However, humorous online videos were noted by participants as a significant way to avoid stigma and enable the sharing of sexual health information. The young people in our study were interested in sexual health information, but did not want to access it at the cost of their own sense of comfort and belonging in their social networks. Any sexual health promotion within these sites must be understood as a site-specific intervention.

Concepts: Epidemiology, Sociology, Sexually transmitted disease, Human sexual behavior, Social information processing, Sexual network, Social network service, United Nations Population Fund


The networks of sexual contacts together with temporal interactions play key roles in the spread of sexually transmitted infections. Unfortunately, data for this kind of network is scarce. One of the few exceptions, the “Romantic network”, is a complete structure of a real sexual network in a high school. Based on many network measurements the authors of the work have concluded that it does not correspond to any other model network. Regarding the temporal structure, several studies indicate that relationship timing can have an effect on the diffusion throughout networks, as relationship order determines transmission routes. The aim is to check if the particular structure, static and dynamic, of the Romantic network is determinant for the propagation of an STI. We performed simulations in two scenarios: the static network where all contacts are available and the dynamic case where contacts evolve over time. In the static case, we compared the epidemic results in the Romantic network with some paradigmatic topologies. In the dynamic scenario, we considered the dynamics of formation of pairs in the Romantic network and we studied the propagation of the diseases. Our results suggest that although this real network cannot be labeled as a Watts-Strogatz network, it is, in regard to the propagation of an STI, very similar to a high disorder network. Additionally, we found that: the effect that any individual contacting an externally infected subject is to make the network closer to a fully connected one, the higher the contact degree of patient zero the faster the spread of the outbreaks, and the epidemic impact is proportional to the numbers of contacts per unit time. Finally, our simulations confirm that relationship timing severely reduced the final outbreak size, and also, show a clear correlation between the average degree and the outbreak size over time.

Concepts: AIDS, Epidemiology, Infectious disease, Infection, The Network, Sexually transmitted disease, Human sexual behavior, Sexual network


Young Black men who have sex with men (YBMSM) experience persistently high rates of undiagnosed HIV and other sexually transmitted infections (STIs) and testing rates remain sub-optimal. Home-based testing (HBT) has been found to be acceptable among MSM and while awareness about HBT is relatively high, uptake has been low. Peer-based approaches have been shown to be effective in reducing HIV risk behavior, yet have not been used to increase utilization of HBT. The purpose of this study was to assess acceptability and feasibility of a program to train YBMSM as Peer Mentors to use and promote HIV and STI home-based testing and specimen collection to their social network members. Fifteen YBMSM ages 18-30 completed in-depth structured interviews and were asked to talk with their social network members about home-based testing. Participants reported acceptability of the Peer Mentor role and two-thirds had conversations with diverse social network members (e.g., male and female, sex partners, friends, family). Facilitators of peer outreach included the novelty of home-based testing, confidence about accuracy of the tests, and resources for linkage to care. Barriers included concerns about negative responses and disclosure of sexual identity/behavior. Results of this study suggest that YBMSM are willing and able to promote HBT to their social networks. This is a promising approach to increasing dissemination of HBT kits for both HIV and STI testing.

Concepts: AIDS, Sexual intercourse, Oral sex, Sexually transmitted disease, Human sexual behavior, Human sexuality, Chlamydia infection, Sexual network


HIV diagnoses among females in the USA declined 40% during 2005-2014 with the largest decline (42%) among Black/African Americans. African American females remain disproportionately affected. We explored contributions of STD rates and sexual risk behaviors among African American females, HIV diagnoses among potential male partners, and sexual risk behaviors and viral suppression rates among HIV-positive potential male partners to declining rates of HIV diagnoses among African American females. Results suggest temporal trends in the factors that increase HIV infectiousness and transmissibility within sexual networks, i.e., decreases in rates of other sexually transmitted infections among African American females, decreases in HIV diagnoses among potential male partners, and increases in viral suppression among heterosexual and bisexual HIV-positive potential male partners in care, may explain the decline. Findings highlight a need for future research that provides context to the sexual risk behaviors and sexual network factors in order to continue progress.

Concepts: AIDS, Sexual intercourse, Oral sex, Sexually transmitted disease, Human sexual behavior, Sexually transmitted diseases and infections, Blood donation, Sexual network


Assortative sexual mixing, the tendency for individuals to choose partners with similar characteristics to themselves, may be an important contributor to the unequal distribution of sexually transmitted infections in populations. We analyzed the tendency for assortative mixing on demographic and sexual behaviors characteristics in newly formed young adults dating partnerships.

Concepts: Sexual intercourse, Epidemiology, Biology, Oral sex, Sexually transmitted disease, Human sexual behavior, Human sexuality, Sexual network


Saskatchewan has one of the highest rates of gonorrhea among the Canadian provinces-more than double the national rate. In light of these high rates, and the growing threat of untreatable infections, improved understanding of gonorrhea transmission dynamics in the province and evaluation of the current system and tools for disease control are important.

Concepts: Epidemiology, Sociology, Sexually transmitted disease, Human sexual behavior, Chlamydia infection, Social network, Sexual network, Network theory


Despite widespread interest in the link between social and sexual networks, little research has focused on how social networks influence the progression of intimate relationships (e.g., from holding hands to sexual intercourse). I argue that social networks not only affect individuals' opportunities to meet romantic partners, but also shape the ideal and actual progressions of intimate acts within their relationships. Using data from the National Longitudinal Survey of Adolescent to Adult Health (Add Health), I conduct an optimal matching analysis of adolescents' purported ideal versus actual relationship sequences, which are comprised of romantic and sexual events. Low discrepancy scores indicate that intimate acts in one’s recent relationship were sequenced much as one had desired. Results demonstrate that how students are situated within their schools' broader friendship networks affects their experiences with intimacy: high rank prestige individuals are better able to achieve their ideal relationships, as are individuals with densely knit friendship networks. Additionally, increased gender salience among boys within the socio-centric friendship network is associated with increased discord between desired and actual relationship progressions, but this relationship is mediated by the rareness of the individual’s ideal relationship trajectory.

Concepts: Sociology, Interpersonal relationship, Adolescence, Human sexuality, Networks, Social network, Sexual network, Network theory