Inspired by empirical studies of networked systems such as the Internet, social networks, and biological networks, researchers have in recent years developed a variety of techniques and models to help us understand or predict the behavior of these systems. Here we review developments in this field, including such concepts as the small-world effect, degree distributions, clustering, network correlations, random graph models, models of network growth and preferential attachment, and dynamical processes taking place on networks.

/pdf/the-structure-and-function-of-complex-networks-34deompc9l.pdf

The Structure and Function of Complex Networks

http://www.maths.qmul.ac.uk/%7Elatora/report_06.pdf

Complex networks: Structure and dynamics

The MMWR series of publications is published by the Office of Surveillance, Epidemiology, and Laboratory Services, Centers for Disease Control and Prevention (CDC), U.S. Department of Health and Human Services, Atlanta, GA 30333.

/pdf/sexually-transmitted-diseases-treatment-guidelines-4zaqk3joit.pdf

Sexually transmitted diseases treatment guidelines.

The study of social networks, and in particular the spread of disease on networks, has attracted considerable recent attention in the physics community. In this paper, we show that a large class of standard epidemiological models, the so-called susceptible/infective/removed (SIR) models can be solved exactly on a wide variety of networks. In addition to the standard but unrealistic case of fixed infectiveness time and fixed and uncorrelated probability of transmission between all pairs of individuals, we solve cases in which times and probabilities are nonuniform and correlated. We also consider one simple case of an epidemic in a structured population, that of a sexually transmitted disease in a population divided into men and women. We confirm the correctness of our exact solutions with numerical simulations of SIR epidemics on networks.

/pdf/spread-of-epidemic-disease-on-networks-5axqo45lly.pdf

Spread of epidemic disease on networks.

This 1966 paperback edition of a publication which first appeared in 1963 has by now been widely reviewed as a worthy contribution to the sociological study of deviant behavior. Its current appearance as a paperback is a testimonial both to the quality of the work and to the prominence of deviant behavior in this generation. In general the author places deviance in perspective, identifies types of deviant behavior, considers the role of rule makers and enforcers, and some of the problems in studying deviance. In addition, he develops a sequential model of deviance relying on the concept of career, a concept originally developed in studies of occupations. In his study of a particular kind of deviance, the use of marihuana, the author posits and tests systematically an hypothesis about the genesis of marihuana use for pleasure. The hypothesis traces the sequence of changes in individual attitude

Outsiders Studies in the Sociology of Deviance.

Social networks and infectious disease: the Colorado Springs Study.

The objective of this study was to prospectively study the changes in the social networks of persons at presumably high risk for HIV in a community with low prevalence and little endogenous transmission. 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. 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. 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 of network configuration in the transmission dynamics of HIV. (authors)

Social network dynamics and HIV transmission.

In this study, the authors estimated overall and cause-specific mortality among prostitute women. They recorded information on prostitute women identified by police and health department surveillance in Colorado Springs, Colorado, from 1967 to 1999. The authors assessed cause-specific mortality in this open cohort of 1,969 women using the Social Security Death Index and the National Death Index, augmented by individual investigations. They identified 117 definite or probable deaths and had sufficient information on 100 to calculate a crude mortality rate (CMR) of 391 per 100,000 (95% confidence interval (CI): 314, 471). In comparison with the general population, the standardized mortality ratio (SMR), adjusted for age and race, was 1.9 (95% CI: 1.5, 2.3). For the period of presumed active prostitution only, the CMR was 459 per 100,000 (95% CI: 246, 695) and the SMR was 5.9 (95% CI: 3.2, 9.0). Violence and drug use were the predominant causes of death, both during periods of prostitution and during the whole observation period. The CMR for death by homicide among active prostitutes was 229 per 100,000 (95% CI: 79, 378), and the SMR was 17.7 (95% CI: 6.2, 29.3). Deaths from acquired immunodeficiency syndrome occurred exclusively among prostitutes who admitted to injecting drug use or were inferred to have a history of it. acquired immunodeficiency syndrome; HIV; homicide; mortality; overdose; prostitution; substance abuse, intravenous; violence

/pdf/mortality-in-a-long-term-open-cohort-of-prostitute-women-2lczghad2m.pdf

Mortality in a Long-term Open Cohort of Prostitute Women

To identify factors that influence individual and group transmission of Chlamydia, the authors conducted community-wide contact tracing of chlamydia cases in Colorado Springs, Colorado, from mid-1996 to mid-1997. Case patients identified persons with whom they had had contact during the 6 months preceding diagnosis; contacts were actively sought and offered DNA amplification testing. Sexual contact networks were used to identify "source cases" and "spread cases," permitting estimation of the basic reproduction number (R0) for individuals and groups. Network and epidemiologic factors influencing R0 were assessed using univariate and multivariate procedures. Of 1,309 case patients, 1,131 (86%) were interviewed, and 2,409 contacts were identified. The 1,131 interviewed cases yielded 623.9 computed spread cases, for an overall R0 of 0.55. Few subgroups analyzed yielded a mean R0 exceeding unity-an observation in keeping with routine surveillance information which suggests that chlamydia incidence is declining in Colorado Springs. Concurrency, a network measure of simultaneous partnerships, was the most powerful predictor of transmission. Direct estimation of basic reproduction numbers for chlamydia using contact tracing techniques is feasible and can produce useful data with which to prioritize control efforts, evaluate interventions, and gauge the place of chlamydia on the epidemic continuum.

/pdf/chlamydia-transmission-concurrency-reproduction-number-and-2esjbwu0qz.pdf

Chlamydia Transmission: Concurrency, Reproduction Number, and the Epidemic Trajectory

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 demonstrate residential stability and close social association at preferred sites for nighttime leisure activity (six major sites out of 300 available). Social aggregation is further demonstrated by the length of social contact 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 important of identifiable social groups in the transmission of gonorrhea.

John J. Potterat

Papers

Social networks and infectious disease: the Colorado Springs Study.

Social network dynamics and HIV transmission.

Mortality in a Long-term Open Cohort of Prostitute Women

Chlamydia Transmission: Concurrency, Reproduction Number, and the Epidemic Trajectory

Gonorrhea as a social disease.