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We utilized public health data and a geographic information system (ArcGIS) to study long-distance sexual partnerships (opposite and same sex partnerships) among chlamydia, gonorrhea, and coinfected STI (sexually transmitted infection) cases. The top 10% of relationships among chlamydia and gonorrhea cases and their contacts equaled or exceeded 198 km and 237 km respectively; the top 15% of partnerships among coinfected cases equaled or exceeded 207 km. This research also detected proportionately more long-distance partnerships among gonorrhea cases than among chlamydia cases. Wasserheit and Aral's four-phase model for understanding the impact of control programs on STI incidence over time offers one framework for interpreting these results: as chlamydia was in an early decline phase during the period under study, while gonorrhea had reached a phase of low endemicity, our results could suggest that in later phases of an STI control program, the overall proportion of long-distance relationships among cases and contacts may increase., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Objectives: To determine whether "high-risk" clients occupied important sociometric positions in sexual networks of commercial sex workers and to estimate whether they were more likely to be HIV and STI infected., Goal: To determine whether a classification of high-risk clients could be validated by network analysis., Study Design: We used proxy data on clients collected from a cross-sectional survey of 49 indoor female sex workers., Results: Two types of clients were categorized as high risk, including those who created sexual bridges between sex establishments and those who had sex with most or all the FSW at an establishment. High-risk clients were significantly more central and were more likely to be members of cohesive subgroups than were lower-risk clients. The few known HIV and STI infections were in high-risk clients., Conclusions: It is possible to identify theoretically high-risk commercial sex clients from the network perspective using simple data collection and categorization approaches.

Purpose: Persistence of sexually transmitted infections (STI) in a population is due to the activities of a small proportion of the population with STI, who transmit infection on average to one or more susceptible sex partners during an infectious period. Within these groups, the average number of transmissions by infectious people to susceptible people in a closed group is measured by the reproductive number; a threshold, above which endemic infection is likely occur and below which, in the rest of the population, it is unlikely to occur. We hypothesized that people with repeated bacterial STI's and their sex partners include the theoretical core group and that they differ from singly infected noncore individuals., Methods: Data on infected individuals and nominated sex partners for the years 1990-1992 were extracted from the notifiable disease and health insurance registries in Manitoba, Canada. Individuals with repeated gonorrhea, chlamydia and coinfected infections were compared using logistic regression, and reproductive numbers were calculated using sex partner data., Results: Of the three groups, the coinfected were youngest, and they were largely of aboriginal descent and had the lowest incomes. Repeaters were older; they had higher incomes, and there were fewer aboriginal people in this group. Chlamydia repeaters had even higher incomes, and this group comprised the least number of aboriginal people. The reproductive numbers showed the same gradient; (1.09, 1.01, and 2.41, respectively.), Conclusions: These data show that these groups do not contribute equally to STI endemicity and indicate that sexual network structure affects epidemic thresholds.

Control of sexually transmitted infections and blood-borne pathogens is challenging due to their presence in groups exhibiting complex social interactions. In particular, sharing injection drug use equipment and selling sex (prostitution) puts people at high risk. Previous work examining the involvement of risk behaviours in social networks has suggested that social and geographic distance of persons within a group contributes to these pathogens’ endemicity. In this study, we examine the role of place in the connectedness of street people, selected by respondent driven sampling, in the transmission of blood-borne and sexually transmitted pathogens. A sample of 600 injection drug users, men who have sex with men, street youth and homeless people were recruited in Winnipeg, Canada from January to December, 2009. The residences of participants and those of their social connections were linked to each other and to locations where they engaged in risk activity. Survey responses identified 101 unique sites where respondents participated in injection drug use or sex transactions. Risk sites and respondents’ residences were geocoded, with residence representing the individuals. The sociospatial network and estimations of geographic areas most likely to be frequented were mapped with network graphs and spatially using a Geographic Information System (GIS). The network with the most nodes connected 7.7% of respondents; consideration of the sociospatial network increased this to 49.7%. The mean distance between any two locations in the network was within 3.5 kilometres. Kernel density estimation revealed key activity spaces where the five largest networks overlapped. Here, the combination of spatial and social entities in network analysis defines the overlap of vulnerable populations in risk space, over and above the person to person links. Implications of this work are far reaching, not just for understanding transmission dynamics of sexually transmitted infections by identifying activity “hotspots” and their intersection with each social network, but also for the spread of other diseases (e.g. tuberculosis) and targeting prevention services. [ABSTRACT FROM AUTHOR]

Objective: We previously identified a high prevalence of Hepatitis C (HCV) amongst solvent-using injection drug users (S-IDU) relative to other injection drug users within the same locality. Here we incorporated social network variables to better characterize some of the behavioural characteristics that may be putting this specific subgroup of IDU at elevated disease risk. Methods: A cross-sectional survey of at-risk populations was carried out in Winnipeg, Canada in 2009. Individuals reporting any history of injection drug and/or solvent use were included in the study. Associations between subgroup membership, infection with HCV and HIV and individual and social network variables were examined. Results: In relation to other IDU, S-IDU were more likely to be infected with HCV, to report ever having shared a syringe, and to associate with other IDU. They were further differentiated in terms of their self-reported sexual orientation, ethnicity and in the injection drugs typically used. Conclusion: Solvent use stands as a proxy measure of numerous other characteristics that put this group of IDU at higher risk of infection. Provision of adequate services to ostracized subpopulations may result in wider population-level benefits. [ABSTRACT FROM AUTHOR]

Investigates the spread of sexually transmitted infections by sampling individuals with large sexual networks. Comparison of sample cases in determining the largest networks; Selection of individuals with chlamydia and gonorrhea; Proportion of the coinfected people.