Increases in the rates of sexually transmitted infections (STIs) suggest that control programmes may not be effectively targeting diverse subpopulations. The objective of this investigation was to examine STI transmission within different groups, using both social network analysis and cluster analysis. Routine partner notification data were analysed from individuals diagnosed with, or exposed to an STI in Manitoba. Groups were identified and characterized. Three different clusters of groups were identified, comprised of demographically and clinically distinct individuals. A greater understanding of disease transmission patterns within these groups will aid in the development of targeted education and prevention programmes for all STIs.
Evaluation of a new chromogenic agar medium for detection of Shiga toxin-producing Escherichia coli (STEC) and relative prevalences of O157 and non-O157 STEC in Manitoba, Canada.
This study assesses the detection performance of CHROMagar STEC medium relative to a reference cytotoxin assay and describes the current relative prevalence of O157 and non-O157 Shiga toxin-producing Escherichia coli (STEC) serotypes within the province of Manitoba, Canada. Over a 10-month period, 205 nonfrozen routine stool submissions to Cadham Provincial Laboratory (CPL) were used to assess the performance of CHROMagar STEC. Of the 205 stools, 14 were identified as true positives by a cytotoxin assay, with resultant CHROMagar STEC sensitivity, specificity, and positive predictive and negative predictive values of 85.7%, 95.8%, 60.0%, and 98.9%, respectively. Using a separate panel of 111 STEC strains, CHROMagar STEC was shown to support the growth of 96 (86.5%) isolates. To assess relative prevalence, attempts were made to isolate by any means all STEC strains identified at CPL over a 17-month period. Of 49 isolates (representing 86.0% of all STEC infections detected), only 28.6% were O157 STEC strains. Of the 35 non-O157 STEC strains, 29 were subjected to further molecular analysis. In contrast to earlier results from our area, carriage of stx(2) appears to have increased. Overall, although CHROMagar STEC is not recommended as a primary screen, our results indicate that it is an effective supplemental medium for the isolation of probable STEC strains. Increased isolation of these serotypes is warranted to better understand their prevalence, clinical characteristics, and epidemiology and aid in the development or enhancement of food safety control programs targeting all STEC serotypes.
Division of Sexual Health Promotion and STD Prevention and Control, Centre for Infectious Disease Prevention and Control, Health Canada, Ottawa, Ontario. ann_jolly@hc-sc.gc.ca
This paper summarises the results of the R0 equation in sexually transmitted infection (STI) repeaters in Manitoba, Canada, in the early 1990s, with both concurrent and more recent descriptions of sexual networks in the same population. The research presented provides empirical network and sex partner data to refine definitions of sexual networks and core groups in phase IV epidemics. New challenges for both practice and research are also discussed.
The use of sexual network analysis has the potential to further our understanding of sexually tranmitted disease (STD) epidemics and contribute to the development of more effective targeted control strategies.
To use sexual network analysis to study transmission patterns of chlamydia and gonorrhea in Manitoba, Canada.
Routinely collected case/contact information gathered by public health nurses was used to construct the sexual network.
Components within the sexual network ranged in size from 2 to 82 people. Two types of components, designated radial and linear, were described. Large linear components resembled the theoretical structure of STD core groups. Geographic analysis of the largest components demonstrated the potential for STD transmission between isolated rural communities and within different areas of an urban center.
The application of sexual network analysis on a provincial basis demonstrated the importance of a centralized, coordinated approach to STD control. The analysis highlights the need for a greater understanding of the causative factors promoting the formation of different component types, the homogeneity and heterogeneity of behaviors within and between components, and the temporal stability of these patterns.
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Comment In: Sex Transm Dis. 2001 Jan;28(1):25-811196041
Methods for accessing large sexual networks are essential for investigating the mechanisms for the spread of sexually transmitted infections.
Four samples of cases were compared with the total population to determine which identified the largest networks.
Individuals with positive test results for chlamydia during a 6-month period were selected from a laboratory database and linked with sex partner information from a notifiable disease registry. Sexual networks were constructed for a random sample, people with positive results from two or more tests for chlamydia, people with positive tests results for both gonorrhea and chlamydia, and the preceding two groups combined.
The coinfected people combined with the repeaters yielded the highest proportion (47.8%) of large networks (>10 people), followed by the coinfected people, the repeaters, and finally the random sample.
People coinfected with chlamydia and gonorrhea and those with repeated chlamydial infection present ideal opportunities for both research and prevention.
Research on risk behaviors for sexually transmitted infections (STIs) has revealed that they seldom correspond with actual risk of infection. Core groups of people with high-risk behavior who form networks of people linked by sexual contact are essential for STI transmission, but have been overlooked in epidemiological studies. Social network analysis, a subdiscipline of sociology, provides both the methods and analytical techniques to describe and illustrate the effects of sexual networks on STI transmission. Sexual networks of people from Colorado Springs, Colorado, and from Winnipeg, Manitoba, Canada, infected with chlamydia during a 6-month period were compared. In Winnipeg, 442 networks were identified, comprising 571 cases and 663 contacts, ranging in size from 2 to 20 individuals; Colorado Springs data yielded 401 networks, comprising 468 cases and 700 contacts, ranging in size from 2 to 12 individuals. Taking differing partner notification methods and the slightly smaller population size in Colorado Springs into account, the networks from both places were similar in both size and structure. These smaller, sparsely linked networks, peripheral to the core, may form the mechanism by which chlamydia can remain endemic, in contrast with larger, more densely connected networks, closer to the core, which are associated with steep rises in incidence.
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Cites: Am J Epidemiol. 1983 Jun;117(6):688-946859024
Cites: Am J Public Health. 1998 Oct;88(10):1496-5029772851
Cites: Soc Sci Med. 1985;21(11):1203-163006260
Cites: JAMA. 1990 Jun 20;263(23):3155-92348524
Cites: Am J Epidemiol. 1999 Dec 15;150(12):1331-910604776
Cites: Sex Transm Dis. 2000 Jan;27(1):12-810654862
Cites: Can Commun Dis Rep. 2000 Jun 15;26(12):101-510932390
Cites: Sex Transm Dis. 2000 Sep;27(8):452-510987450
Cites: Sex Transm Infect. 2000 Aug;76(4):268-7211026881
Cites: Sex Transm Dis. 2000 Nov;27(10):600-911099075
Cites: Sex Transm Dis. 2000 Nov;27(10):627-3511099078
Cites: Sex Transm Dis. 2000 Nov;27(10):636-4311099079
Cites: Sex Transm Dis. 2000 Nov;27(10):644-511099080
Cites: Sex Transm Dis. 2001 Jan;28(1):14-2411196040
Cites: Am J Public Health. 1990 Nov;80(11):1338-422240301
Cites: Am J Public Health. 1991 Oct;81(10):1252-81928521
Cites: MMWR Morb Mortal Wkly Rep. 1992 Jan 3;40(51-52):885-81727971
