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

STD/HIV Program, El Paso County Department of Health and Environment, Colorado Springs, CO 80910, USA.
American Journal of Epidemiology (Impact Factor: 5.23). 01/2000; 150(12):1331-9. DOI: 10.1093/oxfordjournals.aje.a009965
Source: PubMed


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.

Download full-text


Available from: John J Potterat, Oct 10, 2015
30 Reads
  • Source
    • "It is well established that younger age of sexual onset is a risk factor for HIV infection (Gregson et al., 2002; Pettifor, 2004; Sarkar et al., 2006; Wand & Ramjee, 2012), other STIs (Celentano et al., 2008; Duncan et al., 1990; Gindi, Erbelding, & Page, 2010; Kaestle, Halpern, Miller, & Ford, 2005), and unintended pregnancy (Ma et al., 2009; Wellings et al., 2001). Furthermore, multiple sexual partnerships are an important determinant of transmission of HIV/STIs (Koumans et al., 2001; Morris & Kretzschmar, 1997; Potterat et al., 1999; Terrault, 2002; Winer et al., 2003). Many nationwide population-based surveys have also demonstrated that such changes in sexual norms are associated with rising incidence of STIs in the United Kingdom (Wellings et al., 2001), unintended pregnancies in the United States (Hofferth, Kahn, & Baldwin, 1987), and induced abortions among adolescents in Japan (Ono-Kihara, 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Thailand has undergone rapid modernization with implications for changes in sexual norms. We investigated sexual behavior and attitudes across generations and gender among a probability sample of the general population of Nonthaburi province located near Bangkok in 2012. A tablet-based survey was performed among 2,138 men and women aged 15-59 years identified through a three-stage, stratified, probability proportional to size, clustered sampling. Descriptive statistical analysis was carried out accounting for the effects of multistage sampling. Relationship of age and gender to sexual behavior and attitudes was analyzed by bivariate analysis followed by multivariate logistic regression analysis to adjust for possible confounding. Patterns of sexual behavior and attitudes varied substantially across generations and gender. We found strong evidence for a decline in the age of sexual initiation, a shift in the type of the first sexual partner, and a greater rate of acceptance of adolescent premarital sex among younger generations. The study highlighted profound changes among young women as evidenced by a higher number of lifetime sexual partners as compared to older women. In contrast to the significant gender gap in older generations, sexual profiles of Thai young women have evolved to resemble those of young men with attitudes gradually converging to similar sexual standards. Our data suggest that higher education, being never-married, and an urban lifestyle may have been associated with these changes. Our study found that Thai sexual norms are changing dramatically. It is vital to continue monitoring such changes, considering the potential impact on the HIV/STIs epidemic and unintended pregnancies.
    Archives of Sexual Behavior 11/2014; DOI:10.1007/s10508-014-0429-5 · 3.53 Impact Factor
  • Source
    • "When one or both individuals in a regular sexual partnership maintain other sexual partners simultaneously (i.e., concurrent partners), risk for HIV transmission is increased [12] [13]. Engaging in multiple or concurrent partnerships has also been associated with the acquisition of STIs, including chlamydia, gonorrhea, and bacterial STIs [14] [15] [16] [17]. Simulation studies have demonstrated that HIV/STI-positive persons who have concurrent partnerships are at risk of transmitting infection to different partners at the same time, and suggest that even small reductions in levels of partner concurrency may have a dramatic impact on HIV/STI transmission through sexual networks in some populations [13]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Belize has the highest rates of HIV infection in Central America and is experiencing a genera-lized epidemic. The Garífuna, a minority ethnic population, is at risk for HIV. This study uses survey data from Garífuna men and women to examine the frequency of multiple partnerships as well as sociodemographic characteristics and behavioral constructs correlated with hav-ing multiple partners. A high proportion of re-spondents reported having multiple partners, but rates were significantly higher for men, and men had a higher mean number of partners than women. A high proportion of respondents re-ported having a sexually transmitted infection (STI) in the last year, with more men reporting a history of STIs than women. Regression results show the importance of improving men and women's perceived susceptibility for HIV and encouraging them to know their HIV status. Re-inforcing a social norm for partner reduction would also benefit men. Study findings support the need for HIV counseling and testing in Garí-funa communities as well as STI prevention, diagnosis and treatment. This study demon-strates that reducing multiple partnerships among Garífuna men and women is critical for reducing the spread of HIV in Belize.
    Health 07/2012; 4(8):474-48248076. DOI:10.4236/health.2012.48076 · 0.51 Impact Factor
  • Source
    • "One aspect of a species’ biology that may significantly impact exposure to pathogens is its mating system, specifically the number of partners with which an individual typically mates during either a single round of reproduction or over the course of its lifetime. Relationships between sexual behavior and sexually transmitted disease have been extensively studied in humans from both empirical and theoretical perspectives [13]–[16]. These studies have revealed that the number of concurrent partners [17], [18] and the amount of time between sexual encounters [19] are critical in determining the overall population level of infection. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Reproductive behavior may play an important role in shaping selection on Major Histocompatibility Complex (MHC) genes. For example, the number of sexual partners that an individual has may affect exposure to sexually transmitted pathogens, with more partners leading to greater exposure and, hence, potentially greater selection for variation at MHC loci. To explore this hypothesis, we examined the strength of selection on exon 2 of the MHC-DQα locus in two species of Peromyscus. While the California mouse (P. californicus) is characterized by lifetime social and genetic monogamy, the deer mouse (P. maniculatus) is socially and genetically promiscuous; consistent with these differences in mating behavior, the diversity of bacteria present within the reproductive tracts of females is significantly greater for P. maniculatus. To test the prediction that more reproductive partners and exposure to a greater range of sexually transmitted pathogens are associated with enhanced diversifying selection on genes responsible for immune function, we compared patterns and levels of diversity at the Class II MHC-DQα locus in sympatric populations of P. maniculatus and P. californicus. Using likelihood based analyses, we show that selection is enhanced in the promiscuous P. maniculatus. This study is the first to compare the strength of selection in wild sympatric rodents with known differences in pathogen milieu.
    PLoS ONE 05/2012; 7(5):e37562. DOI:10.1371/journal.pone.0037562 · 3.23 Impact Factor
Show more