Sevgi O. Aral

Sexual mixing patterns in the spread of gonococcal and chlamydial infections.

OBJECTIVES This study sought to define, among sexually transmitted disease (STD) clinic attendees, (1) patterns of sex partner selection, (2) relative risks for gonococcal or chlamydial infection associated with each mixing pattern, and (3) selected links and potential and actual bridge populations. METHODS Mixing matrices were computed based on characteristics of the study participants and their partners. Risk of infection was determined in study participants with various types of partners, and odds ratios were used to estimate relative risk of infection for discordant vs concordant partnerships. RESULTS Partnerships discordant in terms of race/ethnicity, age, education, and number of partners were associated with significant risk for gonorrhea and chlamydial infection. In low-prevalence subpopulations, within-subpopulation mixing was associated with chlamydial infection, and direct links with high-prevalence subpopulations were associated with gonorrhea. CONCLUSIONS Mixing patterns influence the risk of specific infections, and they should be included in risk assessments for individuals and in the design of screening, health education, and partner notification strategies for populations.

Determinants and Consequences of Sexual Networks as They Affect the Spread of Sexually Transmitted Infections

Because pathogens spread only within the unique context of a sexual union between people when one person is infectious, the other is susceptible to new infection, and condoms are not used to prevent transmission, the epidemiological study of sexually transmitted infections (STIs) is particularly challenging. Social network analysis entails the study of ties among people and how the structure and quality of such ties affect individuals and overall group dynamics. Although ascertaining complete sexual networks is difficult, application of this approach has provided unique insights into the spread of STIs that traditional individual-based epidemiological methods do not capture. This article provides a brief background on the design and assessments of studies of social networks, to illustrate how these methods have been applied to understanding the distribution of STIs, to inform the development of interventions for STI control.

Understanding and responding to disparities in HIV and other sexually transmitted infections in African Americans

Although these health disparities are not unique to STIs; their nature, pattern, and distribution are complex. This complexity is not solely a result of individual risk behaviours. Increasing evidence indicates that disease epidemics, and, consequently, disparities in morbidity rates, are outcomes of the functioning of systems.

Age at first coitus. A marker for risky sexual behavior in women.

This study examines whether riskier sexual behavior or duration of sexual experience explains why women who become sexually active earlier in life have a higher prevalence of sexually transmitted disease (STD). Responses to a self-administered questionnaire on risk behavior from 4,342 single women attending Planned Parenthood clinics in Pennsylvania were analyzed. Logistic regression was used to control for years of sexual activity, race, and amount of education. Women who became sexually active between the ages of 10 and 14 years were almost 4 times more likely to report having 5 or more sexual partners in the past year (OR = 3.8; 95% CI = 2.6-5.6); 3 times more likely to report having sex with bisexual, intravenous drug-using, or human immunodeficiency virus (HIV)-infected men (OR = 3.5; 95% CI = 2.4-5.0); and twice as likely to report a history of STD within the last 5 years (OR = 2.3; 95% CI = 1.8-3.0) compared with women who became sexually active when they were 17 years of age or older. The analysis suggests that age at first intercourse is a useful marker for risky sexual behavior and history of STD.

Infectious syphilis in high-income settings in the 21st century

In high-income countries after World War II, the widespread availability of effective antimicrobial therapy, combined with expanded screening, diagnosis, and treatment programmes, resulted in a substantial decline in the incidence of syphilis. However, by the turn of the 21st century, outbreaks of syphilis began to occur in different subpopulations, especially in communities of men who have sex with men. The reasons for these outbreaks include changing sexual and social norms, interactions with increasingly prevalent HIV infection, substance abuse, global travel and migration, and underinvestment in public-health services. Recently, it has been suggested that these outbreaks could be the result of an interaction of the pathogen with natural immunity, and that syphilis epidemics should be expected to intrinsically cycle. We discuss this hypothesis by examining long-term data sets of syphilis. Today, syphilis in western Europe and the USA is characterised by low-level endemicity with concentration among population subgroups with high rates of partner change, poor access to health services, social marginalisation, or low socioeconomic status.

Crack, sex, and STD

Increasing rates of syphilis, gonorrhea, chancroid, and sexually transmitted human immunodeficiency virus infection appear to be related to crack cocaine use. This article critically reviews 16 epidemiologic studies that examine drug use, sexual behavior, and sexually transmitted disease (STD). Eight studies found an association between crack and STD, one study found no association between crack and STD, and seven studies found STD to be related to other drugs or methods of cocaine use. The exchange of sex for money or drugs was associated with STD in seven studies. Publications that were reviewed have numerous methodologic weaknesses: broader sampling, uninfected comparison groups, and greater specification of drug use and sexual risk behaviors are needed. Further research should compare different drugs and associated sexual behavior and STD to assess the unique risk conferred by crack. Designing effective interventions will require investigation of risk behavior determinants and barriers to health care.

Social networks, risk-potential networks, health, and disease.

Driven in part by recent research in the epidemiology and prevention of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) and other sexually transmitted or blood-borne infections, the topic of social networks has become the focus of considerable interest and discussion. Networks offer the promise of a way to move the analytic focus one step “above” that of the individual, to consider the patterns through which individuals are linked in small groups and through them in large “sociometric” networks. Thus, network approaches offer a way to apply the analytic insights and computerized techniques of systems theories to studies of the flow of social support, social influence, and infectious diseases through populations and, as well, among organizations. Before going on, though, it might be useful to explain what a network is, what kinds of networks are of most interest, and what some key terms used in network analysis are. This can be done in mathematical language, such that a network is a set of nodes plus the set of connections linking some or all of these nodes to each other. It might be more useful, however, to use a few diagrams to explain these concepts in specific contexts relevant to the study of health and disease.

Prevalence and Correlates of Heterosexual Anal and Oral Sex in Adolescents and Adults in the United States

BACKGROUND Heterosexual anal and oral sex are related to the acquisition of sexually transmitted infections, including human immunodeficiency virus infection. We examined the correlates of heterosexual anal and oral sex in the general population, using data from the National Survey of Family Growth. METHODS The sample included 12,571 men and women aged 15-44 years (79% response rate). RESULTS One-third of men and women had ever had anal sex, and three-quarters had ever had oral sex. Condom use during last oral or anal sex was relatively uncommon. In separate models for men and women, having ever had anal sex was associated with white race, age of 20-44 years, and having had a non-monogamous sex partner. White race, age of 20-44 years, being married, and having higher numbers of lifetime sex partners were related to having ever given oral sex in men and women. Giving oral sex was associated with having a non-monogamous sex partner in men. Ever receiving oral sex was associated with white race and a non-monogamous sex partner in men and women. CONCLUSIONS It would be beneficial to track the prevalence of heterosexual anal and oral sex and associated condom use on a more frequent basis.

The natural history of syphilis. Implications for the transmission dynamics and control of infection

Background: Syphilis remains a significant cause of morbidity in many developing countries and in some areas within North America and Europe. Mathematical models of the transmission dynamics of sexually transmitted infections have provided insights of relevance both to the interpretation of observed epidemiological patterns and to the design of control programs. Their use for the study of syphilis has been limited to date. Goals and Study Design: The authors investigated the trans‐mission dynamics of syphilis against a template based on the natural history of infection in individual patients with the aim of (1) identifying gaps in our understanding of the biology of infection, and (2) providing insights of relevance to the design of control policies. Results: Analyses reveal that Treponema pallidum has a moderate to high probability of transmission during contact between susceptible and infectious sexual partners. This, combined with questions over the existence of any immunity to reinfection, helps to ensure the long‐term persistence of syphilis within “core” activity groups. Patterns of treatment in North America are shown to have significantly altered the relative frequency of individuals in the different stages of disease. Conclusions: The analyses emphasize the benefits to be gained from treating infected people early in the primary stage of infection to reduce the effective period during which infected people can transmit to others. This form of treatment is beneficial for both the individual and the community. Treatment has greatly altered the incidence of different disease stages, but the full implications of treatment depend on whether immunity is present.

Social context of sexual relationships among rural African Americans.

Background Reasons for the strikingly increased rates of HIV and other sexually transmitted infections (STIs) among African Americans in the rural Southeastern United States remain unclear. Investigators have devoted little attention to the potential influence of the social and economic context on sexual behaviors. Goal To examine the potential influence of these contextual factors on behaviors that promote the transmission of STIs. Study Design Focus group interviews in which African Americans from rural North Carolina discussed life in their communities and contextual factors affecting sexual behavior. Results Respondents reported pervasive economic and racial oppression, lack of community recreation, boredom, and resultant substance abuse. Many perceived a shortage of black men because of their higher mortality and incarceration rates compared with whites, and believed this male shortage to be partly responsible for the concurrent sexual partnerships that they perceived as widespread among unmarried persons. Conclusion Contextual features including racism, discrimination, limited employment opportunity, and resultant economic and social inequity may promote sexual patterns that transmit STIs.