Richard Rothenberg

Sociometric risk networks and risk for HIV infection.

OBJECTIVES This study examined whether networks of drug-injecting and sexual relationships among drug injectors are associated with individual human immunodeficiency virus (HIV) serostatus and with behavioral likelihood of future infection. METHODS A cross-sectional survey of 767 drug injectors in New York City was performed with chain-referral and linking procedures to measure large-scale (sociometric) risk networks. Graph-theoretic algebraic techniques were used to detect 92 connected components (drug injectors linked to each other directly or through others) and a 105-member 2-core within a large connected component of 230 members. RESULTS Drug injectors in the 2-core of the large component were more likely than others to be infected with HIV. Seronegative 2-core members engaged in a wide range of high-risk behaviors, including engaging in risk behaviors with infected drug injectors. CONCLUSIONS Sociometric risk networks seem to be pathways along which HIV travels in drug-injecting peer groups. The cores of large components can be centers of high-risk behaviors and can become pockets of HIV infection. Preventing HIV from reaching the cores of large components may be crucial in preventing widespread HIV epidemics.

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.

Gonorrhea as a social disease

Gonococcal infection in Colorado Springs, Colorado, is concentrated in about 1% of the population. The social groups at risk are characterized as young, nonwhite, heterosexual, and connected to the military. They exhibit residential proximity by clustering in “core” census tracts; 51% of cases were in four tracts. They domonstrate residential stability and close social association at preferred sites for nighttime leisure activity (six major site out of 300 available). Social aggregation is further domonstrated by the length of social contract prior to sexual contact (45% had known each other for over two months). the neighborhood nature of sexual choices, and the grouping of sexually connected individuals in lots (six lots contained 20% of cases). The force of infectivity, measured in person-days of potential spread of gonorrhea by infected contacts, provides a quantitative assessment of the importance of identifiable social groups in the transmission of gonorrhea.

Oral transmission of HIV.

Early in the AIDS epidemic there was substantial concern over so-called casual or non-sexual transmission of HIV much of it centered on contact with saliva (sharing an eating utensil or toothbrush). Several epidemiologic studies and national AIDS case surveillance data demonstrated that the transmission of HIV depended on contact with infected body fluids primarily blood and semen. Studies of household transmission of HIV involving family members who shared commonplace activities could not demonstrate passage of the virus. As the epidemic unfolded concerns about casual contact abated and widespread major risk factors such as needle-sharing anal sexual contact and transfusion became the primary epidemiologic focus. Another realignment of emphasis may now be taking place. After about 2 decades the transmission of HIV in industrialized nations has showed some signs of amelioration. Recent surveillance data in the United States and Europe demonstrate a declining acceleration in the reporting of new incident cases of AIDS. Over the past 2 years there has been a substantial decline in AIDS deaths attributed largely to new therapeutic developments and continuing reports of declines in risk-taking. A number of continuing concerns remain however. Younger homosexual men may still be evidencing sexual behaviors that place them at risk and the burden of HIV infection in women is growing. (excerpt)

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.

HIV infections in sub-Saharan Africa not explained by sexual or vertical transmission

An expanding body of evidence challenges the conventional hypothesis that sexual transmission is responsible for more than 90% of adult HIV infections in Africa. Differences in epidemic trajectories across Africa do not correspond to differences in sexual behaviour. Studies among African couples find low rates of heterosexual transmission, as in developed countries. Many studies report HIV infections in African adults with no sexual exposure to HIV and in children with HIV-negative mothers. Unexplained high rates of HIV incidence have been observed in African women during antenatal and postpartum periods. Many studies show 20%–40% of HIV infections in African adults associated with injections (though direction of causation is unknown). These and other findings that challenge the conventional hypothesis point to the possibility that HIV transmission through unsafe medical care may be an important factor in Africas HIV epidemic. More research is warranted to clarify risks for HIV transmission through health care.

Pathways to prostitution: The chronology of sexual and drug abuse milestones

To assess the sequence, timing, and prevalence of sexual and illegal drug use milestones in prostitute women, we interviewed 237 prostitutes in the community and 407 comparison women at an STD clinic. Drug use was more commonly reported by prostitutes than comparisons (86% vs. 23%), as was non‐consensual prepubertal sex (32% vs. 13%). Sexual‐ and drug‐related milestones occurred in the same order in both groups, with drug use preceding sexual activity and injecting drug use preceding prostitution. Ninety‐four percent of prostitutes who injected drugs reported noninjectable drug use before prostitution, and 75% of prostitutes who injected drugs reported doing so before beginning prostitution. The age distributions at critical events were similar for prostitutes and comparison women who reported regular drug use. Comparison women who did not report regular drug use were in general older than both these groups at the time of early sexual experience and drug experimentation. However, the ordering of these eve...

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.

Perceived condom norms and HIV risks among social and sexual networks of young African American men who have sex with men

The association between condom norms and unprotected sexual intercourse was examined within social and sexual networks of young African American men who have sex with men (MSM) in an HIV epicenter of the southern United States. We used a chain-link design to recruit 158 young African American men: 95 initial participants, 56 contacts of participants (alters) and 7 contacts of alters. Men in the high-risk group, compared with those in the no-risk group, perceived significantly lower approval concerning condom use in their social and sexual networks. Also, 100 participants could be connected to each other in 86 dyads of social and sexual networks. Within these dyads, men perceived that their friends and acquaintances approved for them to use condoms but that their friends and acquaintances did not use condoms themselves. Low HIV risk behavior appears associated with perceived social norms that support ones use of condoms, even when perceived norms do not support condom use by network members themselves.

The relevance of social network concepts to sexually transmitted disease control.

Many of the concepts of social network analysis have been tacit assumptions of sexually transmitted disease control efforts for decades. With the advent of AIDS in the 1980s, an overt rapprochement between these two fields—previously separated by culture, context, and language—was made. Social network constructs have immediate appeal to disease control workers, who view many diseases as following the conduits of social interactions. STDs and HIV, in turn, provide network analysts and those who model disease transmission with substantial sets of empirical data that test and illuminate theory. Disease control efforts can be enchanced by incorporating network concepts overtly into current practices. Such concepts offer a path to better delineation of groups at risk, to a better understanding of the interaction of personal risk taking and the social context, and to evaluation of control mechanisms.