Coupling infectious diseases, human preventive behavior, and networks--a conceptual framework for epidemic modeling

Human-disease interactions involve the transmission of infectious diseases among individuals and the practice of preventive behavior by individuals. Both infectious diseases and preventive behavior diffuse simultaneously through human networks and interact with one another, but few existing models have coupled them together. This article proposes a conceptual framework to fill this knowledge gap and illustrates the model establishment. The conceptual model consists of two networks and two diffusion processes. The two networks include: an infection network that transmits diseases and a communication network that channels inter-personal influence regarding preventive behavior. Both networks are composed of same individuals but different types of interactions. This article further introduces modeling approaches to formulize such a framework, including the individual-based modeling approach, network theory, disease transmission models and behavioral models. An illustrative model was implemented to simulate a coupled-diffusion process during an influenza epidemic. The simulation outcomes suggest that the transmission probability of a disease and the structure of infection network have profound effects on the dynamics of coupled-diffusion. The results imply that current models may underestimate disease transmissibility parameters, because human preventive behavior has not been considered. This issue calls for a new interdisciplinary study that incorporates theories from epidemiology, social science, behavioral science, and health psychology.     

Social disintegration and the spread of AIDS: thresholds for propagation along 'sociogeographic' networks.

Previous work on the asymptotic spread of HIV infection along a low dimensional 'sociogeographic' network--a social network characteristically embedded within a limited geographic area--is extended to explore threshold conditions under which the infection extends widely beyond an initial set of infected individuals or communities. Results for one dimension suggest that threshold behavior is analogous to a chain reaction with criticality determined conjointly by the susceptibility of individuals within a community to a nexus of behavior conducive to rapid HIV spread and by the probability of transmission between susceptible communities. Once threshold is exceeded, a stochastic reformulation finds the asymptotic rate of transmission between communities may be markedly raised by positive correlation between susceptibility to rapid disease spread within a community and the transmissibility between communities, for example outmigration driven by social disintegration or residential instability arising from inherent structural factors associated with community susceptibility, as with male prostitution. Examination of threshold conditions for higher dimensional sociogeographic networks most likely characteristic of disease spread beyond the 'deep ghettos' now suffering the highest burden of infection suggests it is at least as, and likely more, effective to decrease the fraction of population susceptible to the high risk behavioral nexus as it is to lower the probability of disease transmission between susceptible individuals or communities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Methods and measures for the description of epidemiologic contact networks

This article describes new methods to characterize epidemiologic contact networks that involve links that are being dynamically formed and dissolved. The new social network measures are designed with an epidemiologic interpretation in mind. These methods are intended to capture dynamic aspects of networks related to their potential to spread infection. This differs from many social network measures that are based on static networks. The networks are formulated as transmission graphs (TGs), in which nodes represent relationships between two individuals and directed edges (links) represent the potential of an individual in one relationship to carry infection to an individual in another relationship. Network measures derived from transmission graphs include "source counts," which are defined as the number of prior relationships that could potentially transmit infection to a particular node or individual.     

Social Connectedness and Disease Transmission: Social Organization,Cohesion, Village Context,and Infection Risk in Rural Ecuador

Social networks are typically seen as conduits for the spread of disease and disease risk factors. However, social relationships also reduce the incidence of chronic disease and potentially infectious diseases. Seldom are these opposing effects considered simultaneously. We have shown how and why diarrheal disease spreads more slowly to and in rural Ecuadorian villages that are more remote from the area’s population center. Reduced contact with outside individuals partially accounts for remote villages’ relatively lower prevalence of diarrheal disease. But equally or more important is the greater density of social ties between individuals in remote communities, which facilitates the spread of individual and collective practices that reduce the transmission of diarrheal disease.Studies of the transmission of infectious diseases1,2 often use social networks as maps of direct contact that facilitate person-to-person transmission of pathogens. From this perspective, relationships are increasingly associated with greater individual-level risk.3 The social cohesion and organization embodied in networks is, however, also critical to the functioning of communities,4–6 but researchers typically neglect the influence of these factors on community-level infectious disease risk.Social relationships have long been employed as contacts in transmission models1,7–9 and as protective factors for chronic disease.10,11 However, outside the literature on sexually transmitted diseases12,13 there are few examples of the protective role of social relationships in the epidemiology of infectious diseases.14 Yet individuals in strongly connected, socially cohesive communities are more likely to perceive economic and social interests as shared. Consequently, they may be more motivated and better organized to pursue collective goals such as building and maintaining effective water and sanitary infrastructure.15This means that understanding infectious disease risk at the community level requires understanding not only how certain social networks may spread disease but also how other social networks may influence the infrastructure and behavior that can prevent population-level exposure. We examined 2 types of social networks from the same set of villages to test the hypothesis that increased social network connectedness predicts diminished risk of diarrheal illness, using a sample of 18 villages in rural, northern coastal Ecuador. Figure 1 illustrates our conceptual model.Open in a separate windowFIGURE 1—Postulated conceptual model: effects of social relationships on disease outcomes, Esmeraldas, Ecuador, 2007.Note. Solid arrows illustrate the hypothesized pathway by which remoteness affects risk of infection. Plus or minus signs indicate the directionality of the relationship.We sought to measure specific risk and protective effects of social relationships via survey and social network analysis methods. In the first part of the analysis, we examined the association of village social networks and different routes of exposure to self-reported illness. In the remainder of the analysis, we attempted to explain these associations in terms of factors that affect village social networks (e.g., remoteness) and the mechanisms by which increased social cohesion is linked to diminished illness risk (e.g., improved water sanitation, education).A road was recently built that connects some of these villages to the nearest large town, which has about 5000 inhabitants. Consequently, these villages now vary in their remoteness, measured by distance and time of travel to this trading center. Our previous analysis suggested that increasing remoteness is associated with increasing average degree in village social networks and that increasing average degree is associated with decreased prevalence of diarrheal disease.16 Additionally, the connectivity of villages to communities in and outside the study region decreases with remoteness.17 Consequently, less remote villages have more transient inhabitants and are more socially fragmented and therefore may be less able to build and maintain the water and sanitation infrastructure and promote hygiene practices than are more remote villages. We explicitly tested the relationships among these components, as described in Figure 1.We defined a contact network as a network comprising relationships that are likely to facilitate transmission of pathogens, that is, a structure of connections through which an individual, denoted “ego,” may infect or be infected by his or her network neighbors, denoted “alters.” This network contains all the pathways an infection may follow through the community via direct human contact. In contrast to contact networks, we defined links in sociality networks as connections between people that represent specific types of social engagement. Connections in sociality networks can correspond to casual acquaintance, close friendship and trust, or economic exchange. The presence or absence of these relationships affects infection risk because they often determine whether communities have effective sanitary infrastructure and health services. In this way, more network connections (e.g., friends) may indicate protective social support, instead of increasing exposure, as in a contact-only network.18     

Mechanisms through which drug, sex partner, and friendship network characteristics relate to risky needle use among high risk youth and young adults

Drug injector social networks are a primary social space in which risky needle use behaviors associated with HIV transmission occur, but the mechanisms through which these social networks influence risky needle use are unclear. This study investigated two mechanisms, social support and social regulation, through which injection drug users' social networks might relate to risky needle use behaviors. We investigated how these mechanisms work in three types of social networks, namely, drug user, sex partner, and friendship networks. Data are from a study of HIV risk and protective behaviors of youth and young adults, ages 14-43, in the United States who were injection drug users and/or the sexual partners of users (N = 277). The three types of networks were constructed based on information respondents provided about their drug use partners, sexual partners, and friends. The networks were characterized by structural (i.e., size and density) and interactional (i.e., multiplexity and closeness) characteristics. We conducted tests for mediation using ordered probit models and multiple linear regression. In the drug networks, social regulation partially meditated the relationship between multiplexity and risky needle use (p<.10). In the sex partner networks, emotional support partially mediated the relationship between network size and risky needle use (p<.001), fully mediated the relationship between network closeness and risky needle use (p<.001), and partially mediated the relationship between multiplexity and risky needle use (p<.01). Mediators were not identified in the friendship networks. The findings demonstrate that network mechanisms explaining risky needle use differ for drug user and sex partner networks in ways consistent with the functional nature of each type of network tie.     

Network Environments and Well-Being: An Examination of Personal Network Structure,Social Capital,and Perceived Social Support

ABSTRACT

Previous studies have demonstrated the role of social networks, social capital, and social support in individuals’ well-being. However, the ways in which these related constructs simultaneously influence one’s well-being outcomes and relate to one another have not been closely examined. This study pays particular attention to the structural characteristics of personal networks, distinction between offline and online social capital, and different indicators of well-being outcomes. Based on survey data collected from 574 college students, the study found that two dimensions of personal networks—density and gender homophily—and social capital in the form of offline bonding capital explained perceived social support. Further, perceived social support consistently predicted well-being outcomes and played a mediating role between personal network density and well-being, as well as between offline bonding capital and well-being. The results offer implications for a more nuanced understanding of the role of individuals’ interpersonal and social environments in well-being outcomes.     

Lizzy Kinsey and the Adult Friendfinders: an ethnographic study of Internet sex and pornographic self-display in Hong Kong

This paper investigates web users, their sexual behaviours and self-representations as observed on a sex and dating site. The website concerned is a massive social network for sexual self-display and encourages members to find real-life partners for sex – whether this be casual sex affairs between singles, swinging couples or extra-marital affairs between ‘aba’ (attached but available) individuals and their lovers. The paper analyses the imaging strategies of Chinese and non-Chinese web users in reference to the playful adoption of commonplace notions of sexiness as ‘cybertypes’. The aim is to reflect on these online behaviours as changing sexual culture while also debating the use of libidinal online personalities as a cognitive apparatus within sex research. The paper thus explores sexual identity within social networks as auto-ethnography and the dual identities and boundary-crossing agencies of web-based researchers and their subjects.     

Interdisciplinary approaches in epidemic studies--II: Four geographic models of the flow of contagious disease

Straightforward adaptation of geographical and regional-science models to conceptual modeling of the epidemic spread of a contagious disease is achieved by: using analogies and isomorphisms, and using as a real example the observations made during a well studied epidemic of variola minor (the mild form of smallpox), a typical contagious disease. The adaptation of the Wilson model of planning for urban development includes a static view (network) of the structure and activities of the population and of organizations (diffusion agencies such as day schools), and the dynamic view (mechanism of epidemic spread) which includes the changes with time of elements of the network brough by flow of disease. Adaptation of the Brown model of spatial diffusion yields flows of disease occurring between micro-scale units (households) of social interactions but aggregations of these units do not participate explicitly in the flows. The occurrence of successive generations of affected households is specified as well as the occurrence of definite stages of the epidemic progression. Adaptation of the Alves-Morrill model of spatial diffusion yields a network of social groups and interdependencies; a simplified network of the mechanism of spread that shows flows of disease between individuals grouped into generations of infected individuals and generations of infective individuals; and a more realistic view which shows the flows of disease between real epidemiological units such as households and school classes. Adaptation of the Morrill-Manninen model of spatial diffusion concentrates on the mechanism and parameters having the epidemic spread as output. The interdependencies between the parameters and between each parameter and the epidemic spread are represented, including feedback processes. Brown's model seems to be the best for describing the epidemic spread of contagious disease while the Morrill-Manninen model is the most promising for investigating the detailed mechanism of the spread. Since these two models complement each other, their combined use is indicated.     

Coming untied? Narrative accounts of social network dynamics from first‐time mental health clients

Existing research demonstrates a relationship between mental illness and social network attrition over time – a pattern attributed to dysfunctional psychosocial and interpersonal processes and rejection. Yet, according to the social network perspective, personal network dynamics naturally accompany important biographical transitions or events, suggesting that our current understanding of mechanisms underlying network instability in mental illness may be incomplete. This research uses data from the Indianapolis Network Mental Health Study, a longitudinal study of social network dynamics spanning five years. It focuses on in‐depth interviews with 135 individuals making their first major contact with the mental health treatment system. First, levels of tie attrition and replacement in the core discussion networks of individuals with mental illness are compared to a sample with no self‐reported history of mental illness. Second, using open‐ended responses describing why specific individuals mentioned in previous waves were not listed again, respondents’ explanations of attrition are analysed qualitatively. In addition to providing support for existing perspectives, the themes suggest a need to also consider: (i) interaction strategies that maximise the supportiveness of social networks and minimise burden and (ii) changing life circumstances external to social networks that influence opportunities for social interaction.     

Australian homeless persons’ experiences of social connectedness,isolation and loneliness

Both loneliness and a lack of social integration are associated with serious physical and psychological health issues. One population highly susceptible to social isolation and loneliness are individuals who are homeless, who also experience high rates of mental disorder and relationship breakdown. Despite this, little research has explored how social networks, isolation and loneliness are experienced for those with a history of homelessness. In‐depth, semi‐structured interviews were used to get a nuanced understanding of how social networks and isolation are experienced and understood by individuals experiencing homelessness. Sixteen participants who were either homeless (n = 11) or previously homeless (n = 5) in Sydney, Australia, completed one‐off interviews that were audio‐recorded and transcribed. Data were analysed using thematic analysis. Participants constructed their social networks as being both constrained and enabled by marginalisation. They experienced rejection from the non‐homeless: the loss of critical network members, including rejection from family and a lack of companionship, and low quality and precarious relationships within the homeless community. These accounts were best conceptualised through loneliness theory. Participant's accounts signal that the homeless will likely continue feeling isolated if mainstream attitudes towards homelessness remain stigmatising and discriminatory.     

Raising the level of analysis of food-borne outbreaks: food-sharing networks in rural coastal Ecuador

OBJECTIVES: Consuming contaminated food is a well-documented individual-level risk factor for diarrheal disease. The sharing of food also influences the distribution of diarrheal disease risk through a community and region. Understanding this social process at a population level is therefore an important dimension of risk not captured by standard individual-level analyses. We examined social networks related to food-sharing in rural villages at 2 scales: within a village, examining whether connections within these networks clustered or were uniformly spread; and among villages, looking at whether food-sharing networks differed according to the village's remoteness from a population center. METHODS: We surveyed 2129 individuals aged 13 years and older in 2003-2004, within a representative (block-randomized) sample of 21 rural villages in Esmeraldas province, northern coastal Ecuador. We calculated degree (number of social contacts) for a social network defined by sharing food. RESULTS: Networks of households sharing food differ according to remoteness from a metropolitan center. On average, residents living in "far villages" had 2 more social contacts than those in "close villages," and 12 more years of residence in their village. Estimates of transmissibility (a measure of outbreak potential) based on network structure varied as much as 2-fold across these villages. CONCLUSIONS: Food-sharing practices link particular households in rural villages and have implications for the spread of food-borne pathogens. The food-sharing networks in remote rural villages are heterogeneous and clustered, consistent with contemporary theories about disease transmitters. Network-based measures may offer tools for predicting patterns of disease outbreaks, as well as guidance for interventions.     

Quality assurance as a managerial innovation: a research perspective.

Quality assurance is defined and concepts from innovation theory are applied to the study of quality assurance programs. Two distinct although not mutually exclusive perspectives on innovation are considered--the diffusion perspective, focusing on the innovation itself and its implementation, and the adoption perspective, highlighting factors characteristic of the adoption unit (i.e., the organization or individuals within it) that facilitate or impede the adoption process. Directions for future research are suggested.     

From theory to practice: identifying authentic opinion leaders to improve care

Diffusion of Innovations and Opinion Leader theories can be translated into practical applications to improve health care delivery and financial performance by applying them to influence referral patterns and decrease variations in care. Health care organizations can rapidly spread "better practices" to their practicing physicians by understanding the social and communication networks that are naturally developed by those practitioners. Physicians view this diffusion process as promoting autonomy, and as a legitimate approach to adoption of information needed in daily practice.     

Social networks, ideation, and contraceptive behavior in Bangladesh: a longitudinal analysis

Longitudinal survey data from a panel of married women in Bangladesh is used to estimate the impact of a social network approach to family planning field worker communication and to test a theoretical model of behavior change that explains why women adopt modern contraceptives. Government field workers were trained to organize group discussions with women in the homes of opinion leaders located at central points in each village's social network. A set of intervening variables, referred to collectively as 'ideation', are derived from diffusion of innovation and social network theory to explain how the social network approach affects contraceptive behavior. The rate of increase in modern contraceptive use was found to be five times greater among women in the social network approach than among women who were visited by field workers at home. The impact of the social network approach on modern contraceptive use was almost double that of conventional field worker visits after controlling for the effects of prior contraceptive use and intention, prior home visits, and selected socio-demographic characteristics. Both approaches had the same degree of impact on ideation. The results confirm the influence of ideation on fertility change and suggest that family planning programs would benefit from training field workers to use a social network approach.     

通过HIV溯源和分子网络分析推动艾滋病精准发现与防控

当前我国新发现HIV感染者经性传播模式较为复杂。开展HIV溯源和分子网络分析,尽可能早期发现传染源并开展精准防控,对遏制艾滋病传播具有重大意义。本期重点号结合目前HIV溯源、分子网络分析、精准发现与精准防控进展,重点报告2017-2020年宁波市HIV/AIDS流行病学特征,通过HIV溯源调查分析HIV/AIDS与其性伴的HIV传播关系,将社会网络和分子网络相结合分析HIV传播模式,为我国艾滋病精准发现和精准防控的应用型研究提供科学依据,推动我国艾滋病的科学防控。     

Involvement of the Personal Social Network as a Factor in Parent Education Effectiveness

This study examined the impact of mothers' involvement with their social networks upon their self‐reported changes in behaviors and attitudes due to a parenting intervention—in this case monthly, age‐paced parenting newsletters. Path analyses revealed that discussing and sharing newsletter copies with others was associated with greater self‐reported change but did not significantly mediate the relationship between newsletter use and parental change. Rather, individual use of the newsletter and social sharing of the content had independent effects on parenting. The results support a general view that the advice of parenting programs is not accepted or rejected in a vacuum, but often within the context of discussions within the participants' existing social networks. This suggests two practical implications for program developers: (a) Interventions might be more effective if they encouraged such social network processing of program advice, and (b) programs might even target social networks rather than individual parents as their clients.