Kirk Dombrowski

Theory, measurement and hard times: some issues for HIV/AIDS research.

Economic and political instability and related “big events” are widespread throughout the globe. Although they sometimes lead to epidemic HIV outbreaks, sometimes they do not—and we do not understand why. Current behavioural theories do not adequately address these processes, and thus cannot provide optimal guidance for effective intervention. Based in part on a critique of our prior “pathways” model of big events, we suggest that cultural–historical activity theory (CHAT) may provide a useful framework for HIV research in this area. Using CHAT concepts, we also suggest a number of areas in which new measures should be developed to make such research possible.ResumenLa inestabilidad económica y política y los “grandes eventos” asociados con ella están muy extendidas en todo el mundo. Los “grandes eventos” a veces conducen a brotes epidémicos de VIH, y a veces no, y no entendemos por qué. Las actuales teorías del comportamiento no abordan adecuadamente estos procesos, y por lo tanto no pueden proveer una óptima orientación para una efectiva intervención. Basándonos en parte en una crítica a nuestro modelo de las “vías” que se interconectan durante los grandes eventos, sugerimos que la Teoría de la Actividad Histórico-Cultural (CHAT en ingles) puede proporcionar un marco útil para la investigación del VIH en esta área. Utilizamos conceptos de CHAT y también sugerimos una serie de áreas en las que las nuevas medidas se deben desarrollar para hacer posible este tipo de investigación.

A reexamination of connectivity trends via exponential random graph modeling in two IDU risk networks.

Patterns of risk in injecting drug user (IDU) networks have been a key focus of network approaches to HIV transmission histories. New network modeling techniques allow for a reexamination of these patterns with greater statistical accuracy and the comparative weighting of model elements. This paper describes the results of a reexamination of network data from the SFHR and P90 data sets using Exponential Random Graph Modeling. The results show that “transitive closure” is an important feature of IDU network topologies, and provides relative importance measures for race/ethnicity, age, gender, and number of risk partners in predicting risk relationships.

Hepatitis C virus infection among HIV-positive men who have sex with men: protocol for a systematic review and meta-analysis

BackgroundOutbreaks of hepatitis C virus (HCV) infection have been reported in HIV-positive men who have sex with men (MSM) in North America, Europe and Asia. Transmission is believed to be the result of exposure to blood during sexual contact. In those infected with HIV, acute HCV infection is more likely to become chronic, treatment for both HIV and HCV is more complicated and HCV disease progression may be accelerated. There is a need for systematic reviews and meta-analyses to synthesize the epidemiology, prevention and methods to control HCV infection in this population.Methods/designEligible studies will include quantitative empirical data related to sexual transmission of HCV in HIV-positive MSM, including data describing incidence or prevalence, and associations between risk factors or interventions and the occurrence or progression of HCV disease. Care will be taken to ensure that HCV transmission related to injection drug use is excluded from the incidence estimates. Scientific databases will be searched using a comprehensive search strategy. Proceedings of scientific conferences, reference lists and personal files will also be searched. Quality ratings will be assigned to each eligible report using the Newcastle–Ottawa scale. Pooled estimates of incidence rates and measures of association will be calculated using random effects models. Heterogeneity will be assessed at each stage of data synthesis.DiscussionHIV-positive MSM are a key HCV-affected population in the US and other high-income countries. This review seeks to identify modifiable risk factors and settings that will be the target of interventions, and will consider how to constitute a portfolio of interventions to deliver the greatest health benefit. This question must be considered in relation to the magnitude of HCV infection and its consequences in other key affected populations, namely, young prescription opioid users who have transitioned to illicit opiate injection, and older injection drug users among whom HCV prevalence and incidence are extremely high. This review is part of a series of systematic reviews and meta-analyses that will synthesize the evidence across all these population groups and develop recommendations and decision tools to guide public health resource allocation.Trial registrationPROSPERO registration number: CRD42013006462

Out on the Land: Income, Subsistence Activities, and Food Sharing Networks in Nain, Labrador

In recent Inuit ethnography, a major concern has been how and to what extent contemporary Inuit participate in and depend on subsistence activities, particularly in the context of increasing wage employment and growing participation in the cash economy. This paper provides an analysis of these activities in the predominately Inuit community of Nain, Labrador. Using social network data and demographic information collected between January and June 2010, we examine the interconnections between subsistence activities—obtaining “country food” through activities such as hunting, fishing, and collecting—with access to the means of obtaining subsistence resources (such as snow mobiles, cabins, and boats), employment status, and income. Our data indicate that individuals with higher employment status and income tend to be more central to the network of subsistence food sharing, but not because they have greater access to hunting tools or equipment (they do not). We conclude that those individuals who play the most central role in the network are those who are financially able to do so, regardless of access to hunting tools/means.

Kinship, Family, and Exchange in a Labrador Inuit Community

Kinship, family, and household have received considerable attention in Inuit studies; this paper takes a comparative social networks approach to these issues. Here kinship connections are represented in network form as a composite of individual kinship dyads of descent, coparentage, or siblingship. The composite kinship network is then used as a standard of measure for the pair-wise distances of exchange/dependency dyads appearing in other social networks within the community (including the country-food distribution network, store-bought-food-sharing network, traditional-knowledge network, alcoholco-use network, household-wellness networks, job-referrals network, and the housing network). This analysis allows us to gauge the role that kinship (of various distances, including household and family) plays in structuring exchanges across these various network domains. The data used here was collected in Nain, Labrador in January– June 2010. From 330 interviews, we extracted more than 4,900 exchanges and patterns of helping relationships among the 749 current adult residents of the community, and more than 10,000 kinship connections among a total of 1,687 individuals directly linked by descent, marriage or coparentage. The results of this analysis show that past emphasis on kin-oriented exchange in Inuit communities has mistakenly emphasized the nature of the exchange item (traditional versus store-bought (cash) economy) thereby missing important data on the nature of the exchange itself (reciprocal or one-way).

The Interaction of Risk Network Structures and Virus Natural History in the Non-spreading of HIV Among People Who Inject Drugs in the Early Stages of the Epidemic

This article explores how social network dynamics may have reduced the spread of HIV-1 infection among people who inject drugs during the early years of the epidemic. Stochastic, discrete event, agent-based simulations are used to test whether a “firewall effect” can arise out of self-organizing processes at the actor level, and whether such an effect can account for stable HIV prevalence rates below population saturation. Repeated simulation experiments show that, in the presence of recurring, acute, and highly infectious outbreaks, micro-network structures combine with the HIV virus’s natural history to reduce the spread of the disease. These results indicate that network factors likely played a significant role in the prevention of HIV infection within injection risk networks during periods of peak prevalence. They also suggest that social forces that disturb network connections may diminish the natural firewall effect and result in higher rates of HIV.ResumenEste artículo explora cómo las dinámicas de redes sociales pueden haber reducido la propagación de la infección por VIH-1 entre las personas que se inyectan drogas durante los primeros años de la epidemia. Estocásticas, eventos discretos, las simulaciones basadas en agentes se utilizan para probar la de si un “efecto cortafuegos” puede surgir de los procesos de auto-organización, al nivel de actor, y si este efecto puede dar cuenta de las tasas estables de la prevalencia del VIH por debajo de la saturación de la población. Repetidos experimentos de simulación muestran que, en la presencia de brotes recurrentes, agudos, y altamente infecciosos, las estructuras micro-red se combinan con la historia natural del virus del VIH para reducir la propagación de la enfermedad. Estos resultados indican que los factores de la red probablemente jugaron un papel importante en la prevención de la infección por el VIH dentro de las redes de riesgo de inyección durante los períodos de pico de prevalencia. Además, sugieren que las fuerzas sociales que perturban las conexiones de red pueden disminuir el efecto cortafuegos natural y resultan en tasas más altas de VIH.

Improving the Network Scale-Up Estimator: Incorporating Means of Sums, Recursive Back Estimation, and Sampling Weights.

Researchers interested in studying populations that are difficult to reach through traditional survey methods can now draw on a range of methods to access these populations. Yet many of these methods are more expensive and difficult to implement than studies using conventional sampling frames and trusted sampling methods. The network scale-up method (NSUM) provides a middle ground for researchers who wish to estimate the size of a hidden population, but lack the resources to conduct a more specialized hidden population study. Through this method it is possible to generate population estimates for a wide variety of groups that are perhaps unwilling to self-identify as such (for example, users of illegal drugs or other stigmatized populations) via traditional survey tools such as telephone or mail surveys—by asking a representative sample to estimate the number of people they know who are members of such a “hidden” subpopulation. The original estimator is formulated to minimize the weight a single scaling variable can exert upon the estimates. We argue that this introduces hidden and difficult to predict biases, and instead propose a series of methodological advances on the traditional scale-up estimation procedure, including a new estimator. Additionally, we formalize the incorporation of sample weights into the network scale-up estimation process, and propose a recursive process of back estimation “trimming” to identify and remove poorly performing predictors from the estimation process. To demonstrate these suggestions we use data from a network scale-up mail survey conducted in Nebraska during 2014. We find that using the new estimator and recursive trimming process provides more accurate estimates, especially when used in conjunction with sampling weights.

A stochastic agent-based model of pathogen propagation in dynamic multi-relational social networks

We describe a general framework for modeling and stochastic simulation of epidemics in realistic dynamic social networks, which incorporates heterogeneity in the types of individuals, types of interconnecting risk-bearing relationships, and types of pathogens transmitted across them. Dynamism is supported through arrival and departure processes, continuous restructuring of risk relationships, and changes to pathogen infectiousness, as mandated by natural history; dynamism is regulated through constraints on the local agency of individual nodes and their risk behaviors, while simulation trajectories are validated using system-wide metrics. To illustrate its utility, we present a case study that applies the proposed framework towards a simulation of HIV in artificial networks of intravenous drug users (IDUs) modeled using data collected in the Social Factors for HIV Risk survey.

Network sampling of social divisions in a rural Inuit community

This paper describes results from a network survey of Nain – a predominantly Inuit community of ~1200 people located on the northern coast of Labrador. As part of a larger social network research project, we used peer-referral sampling to recruit 330 residents for interviews about food sharing, housing, public health and community traditions. The peer-referral chains were analysed statistically to determine the presence and absence of social divisions in the community. The results of these analyses show that ethnic identification, relocation status and household income were the most significant social divisions in the community, while gender, education level and employment status show little or no effect on patterns of between-group interconnection. We argue that statistical patterns in the presence (and absence) of intergroup links offer novel ways to examine the interrelationship between recent economic development and the historical disruptions caused by Inuit community relocations in the 1950s.

Hepatitis C serosorting among people who inject drugs in rural Puerto Rico

Due to the high cost of treatment, preventative measures to limit Hepatitis C (HCV) transmission among people who inject drugs (PWID) are encouraged by many public health officials. A key one of these is serosorting, where PWID select risk partners based on concordant HCV status. Research on the general U.S. population by Smith et al. (2013) found that knowledge of ones own HCV status facilitated serosorting behaviors among PWID, such that respondents with knowledge of their own status were more likely to ask potential partners about their status prior to sharing risk. Our objective was to see if this held true in rural Puerto Rico. We replicate this study using a sample of PWID in rural Puerto Rico to draw comparisons. We used respondent driven sampling to survey 315 participants, and have a final analytic sample of 154. The survey was heavily modeled after the National HIV Behavioral Survey, which was the dataset used by the previous researchers. We found that among PWID in rural Puerto Rico, unlike in the general population, knowledge of ones own HCV status had no significant effect on the selection of ones most recent injection partner, based on his/her HCV status. We conclude that PWID in rural Puerto Rico differ from the general U.S. population when it comes to serosorting behaviors, and that these differences should be taken into account in future outreaches and intervention strategies.