Alden S. Klovdahl

Social networks and the spread of infectious diseases: The AIDS example

Conceptualizing a population as a set of individuals linked together to form a large social network provides a fruitful perspective for better understanding the spread of some infectious diseases. Data related to AIDS (the acquired immune deficiency syndrome) were used to illustrate the potential usefulness of a network approach in evaluating the infectious agent hypothesis when studying a disease or disease outbreak of unknown etiology and in developing strategies to limit the spread of an infectious agent transmitted through personal relationships.

Social networks and infectious disease: The Colorado Springs study

The social network paradigm provides a set of concepts and methods useful for studying the structure of a population through which infectious agents transmitted during close personal contact spread, and an opportunity to develop improved disease control programs. The research discussed was a first attempt to use a social network approach to better understand factors affecting the transmission of a variety of pathogens, including hepatitis B virus (HBV) and human immunodeficiency viruses (HIV), in a population of prostitutes, injecting drug users (IDU) and their personal associates in a moderate-sized city (Colorado Springs, CO). Some of the challenges of studying large social networks in epidemiological research are described, some initial results reported and a new view of interconnections in an at risk population provided. Overall, for the first time in epidemiologic research a large number of individuals (over 600) were found connected to each other, directly or indirectly, using a network design. The average distance (along observed social relationships) between persons infected with HIV and susceptible persons was about three steps (3.1) in the core network region. All susceptibles in the core were within seven steps of HIV infection.

Social network dynamics and HIV transmission.

Objective:To prospectively study changes in the social networks of persons at presumably high risk for HIV in a community with low prevalence and little endogenous transmission. Methods:From a cohort of 595 persons at high risk (prostitutes, injecting drug users, and sexual partners of these persons) and nearly 6000 identified contacts, we examined the social networks of a subset of 96 persons who were interviewed once per year for 3 years. We assessed their network configuration, network stability, and changes in risk configuration and risk behavior using epidemiologic and social network analysis, and visualization techniques. Results:Some significant decrease in personal risk-taking was documented during the course of the study, particularly with regard to needle-sharing. The size and number of connected components (groups that are completely connected) declined. Microstructures (small subgroups of persons that interact intensely) were either not present, or declined appreciably during the period of observation. Conclusions:In this area of low prevalence, the lack of endogenous transmission of HIV may be related in part to the lack of a network structure that fosters active propagation, despite the continued presence of risky behaviors. Although the relative contribution of network structure and personal behavior cannot be ascertained from these data, the study suggests an important role for network configuration in the transmission dynamics of HIV.

Mapping a social network of heterosexuals at high risk for HIV infection

Objective:To determine how heterosexuals at risk for HIV infection interconnect in social networks and how such relationships affect HIV transmission. Design:Cross-sectional study with face-to-face interviews to ascertain sociosexual connections; serologic testing. Participants:Prostitute women (n=133), their paying (n=129) and non-paying (n=47) male partners; injecting drug users (n= 200) and their sex partners (n=41). Participants were recruited in sexually transmitted disease and methadone clinics, an HIV-testing site, and through street outreach in Colorado Springs, Colorado, USA. Main outcome measures:Reported behaviors, risk perceptions, sociosexual linkages, and HIV prevalence. Results:Respondents were well informed, but reported engaging in high-risk behaviors frequently. Nevertheless, over 70% of respondents perceived themselves to be at low risk for HIV infection. The 595 respondents identified a social network of 5162 people to which they belonged. Network analytic methods indicated 147 separate connected components of this network; eight of the 19 HIV-positive individuals in the network were located in smaller components remote from the largest connected component. Conclusion:The isolated position of HIV-positive individuals may serve as a barrier to HIV transmission and may account for the lack of diffusion of HIV in heterosexual populations in this region. Network analysis appears useful for understanding the dynamics of disease transmission and warrants further development as a tool for intervention and control.

Choosing a centrality measure: Epidemiologic correlates in the Colorado Springs study of social networks☆

Abstract In a continuing analysis of a large network of persons who practice risky behaviors in an area of low prevalence for HIV transmission, we compared eight measures of centrality. Although these measures differ in their theoretical formulation and their distributional forms, they demonstrated substantial concordance in ranking as noncentral all but one of the HIV-positive persons in a large connected component of 341 persons, providing further support for the role of network structure in disease transmission.

A note on images of networks

Abstract Visual imagery and visual representations have proven very useful in some of the most important discoveries in the history of science. It is not surprising, therefore, that the earliest students of network phenomena often made use of visual representations (e.g. sociograms) to assist in the analysis, interpretation and illustration of complex relational data: by creating such visual representations, human faculties for visual imagery and pattern recognition could be more fully utilized in the search for structural patterns in sociometric networks. What is somewhat surprising, though, is that the techniques for creating visual representations of relational data have remained virtually unchanged since the study of social networks began: the slow, tedious, pen-and-ink approach of forty years ago is still very much the method of the day. Readily available computer graphics technology, however, introduces potentially powerful possibilities, and some of these are explored. The results of this initial exploration suggest that the time is ripe for forging new tools that will facilitate the analysis of complex relational data, stimulate the development of network theory, and provide new perspectives from which to view previously hidden facets of society.

Social network research and human subjects protection: Towards more effective infectious disease control

Abstract The issue of human subject protection in relation to social network research on the spread and control of human pathogens is considered. As this area derives most of its concepts and methods from social network analysis more generally, the present discussion has wider relevance. One problem is that some Institutional Review Boards (IRBs) have assumed that if a participant (who gave informed consent) is to be asked to name network associates these too — automatically — would be human subjects from whom informed consent also must be obtained. Invariably, if this occurs proposed research — whatever its funding and potential contributions might be — is blocked. A conservative approach is taken here. The Common Rule is assumed to provide relevant guidance, the responsibility of IRBs is to make decisions based on the Common Rule, and in consequence the burden is on those proposing social network research to design — and defend — their planned work with this in mind. At the same time, it is argued that it is important not to stifle beneficial research by adding to one inherently conservative review process (of grant proposals) another (of IRBs) so that work is prevented simply because it is research at the frontiers rather than ‘safe’ research.

Spatial Bridging in a Network of Drug-Using Male Sex Workers

This study sought to determine whether drug-using male sex workers (MSWs) spatially bridge sexual networks across cities and to determine whether the behaviors of MSWs who bridge differ from the behaviors of those who do not. Data were collected from 42 MSWs in Houston, Texas, between May 2003 and February 2004. Spatial bridging was defined as having traded sex for money in another city before traveling to and trading in Houston. Cities bridged by MSWs were geographically plotted and were primarily located in the Gulf Coast and in Florida. Slightly less than half of MSWs were identified as spatially bridging from one city to another. A significantly higher proportion of MSWs who bridged cities were homosexual (55% vs. 23%) and HIV positive (31% vs. 5%). Those who bridged cities used marijuana and injected drugs more frequently and had significantly more male sex partners than MSWs who did not bridge cities. Despite the small sample size, this study found that many drug-using MSWs spatially bridge sexual networks in cities where they trade sex for money.

Social Networks in an Urban Area: First Canberra Study1

However, studies of social interaction in cities have often given rise to enticing theoretical questions which it has not been possible to answer. More specifically, a growing number of studies provide information about ’ego networks’-about individual urban residents and those with whom each is in direct contact-but leave unanswered questions as to whether such (ipso facto disconnected) network segments are really tied together in some manner, and if so how. For example, Martin (1970) studied the social ties of residents of three Adelaide suburbs, and found that it was not uncommon for two respondents, each living in a different

Using knowledge of social networks to prevent human immunodeficiency virus infections : The Colorado Springs study

Abstract The development of an applied social science research project with implications for the management of infectious diseases is described. The project evolved out of a multidisciplinary effort to understand how sexually transmissible agents enter into social systems, are transmitted and can be identified, prevented and controlled. Collaborators began their investigations in the 1970s by looking at the social and behavioral patterns of individuals infected with gonorrhea, then applied similar methods in the late 1980s and early 1990s to examine the ways human immunodeficiency virus (HIV), the pathogen that causes AIDS, might spread among heterosexuals in a mid-sized American community. Concepts of personal and social networks of individuals linked by social, sexual and drug-sharing exposures guided the systematic collection of information from 595 participants in a large, prospective study. Results suggest that HIV did not spread among heterosexuals who engaged in risky sexual and needle-sharing beha...