229 results found
Boily MC, Lowndes C, Alary M, 2002, The impact of HIV epidemic phases on the effectiveness of core group interventions: insights from mathematical models., Pages: i78-i90, ISSN: 1368-4973
Mathematical models have highlighted the disproportionate contribution of core group transmitters to the spread of sexually transmitted diseases. Because the effectiveness of interventions varies with time, it has been suggested that epidemic phases should be considered in the design of prevention strategies. This study aimed to examine the impact of HIV epidemic phases on the effectiveness of HIV interventions based on gonorrhoea screening and condom use, targeted to core groups. The results are based on a mathematical model of gonorrhoea and HIV transmission in a relatively slow spreading HIV epidemic using Cotonou (Benin) as an example. For epidemics with a low reproductive potential modest core group interventions can significantly reduce HIV incidence and prevalence. As the epidemic matures, effective interventions should also incorporate core and non-core populations. For epidemics with a high reproductive potential, core group interventions are necessary but not sufficient to have a rapid and large scale impact. A more general population approach is also needed early in the epidemic. Epidemic phases are also important in the evaluation of prevention strategies.
poulin C, ALARY M, Bernier F, et al., 2001, Prevalence of Chlamydia trachomatis and Neisseria gonorrhoeae Among At-Risk Women, Young Sex Workers, and Street Youth Attending Community Organizations in Quebec City, Canada, Sexually Transmitted Diseases:, Vol: 28, Pages: 437-443
Background: Despite a relatively recent decline in the global incidence of Chlamydia trachomatis and Neisseria gonorrhoeae it seems that some segments of the population such as street youth, sex workers, and individuals with social problems or delinquent behavior could be part of a core group for STDs. These persons may be reluctant to undergo STD diagnosis in traditional medical settings.Goals: To determine the prevalence of C trachomatis and N gonorrhoeae infection using polymerase chain reaction on urine samples among subjects attending an anonymous HIV testing clinic and four community organizations in Quebec City, and to identify associated risk factors.Study Design: A cross-sectional study of 626 street youth, sex workers, and women with social problems or delinquent behavior was conducted.Results: The prevalences of N gonorrhoeae and C trachomatis were, respectively, 1.1% (95% CI, 0.5%-2.3%) and 5.8% (95% CI, 4.1%-7.9%). No significant difference was found between men and women, but the sexually transmitted disease (STD) prevalence was much higher in subjects younger than 20 years: 11.4% versus 3.6% (P < 0.01). In a logistic regression model, factors independently associated with STD infection were age younger than 20 years (OR, 2.6;P = 0.007), occasional sex partners (OR, 2.9;P = 0.007), and injection of drugs (OR, 2.8;P = 0.002) in the preceding 6 months.Conclusions: A moderate STD prevalence was found in the study population. The prevalence, however, can be considered high (>10%) among street youth and young sex workers. Providing community-based STD screening and treatment services appear to be an efficient method for reaching these high-risk groups.
Boily MC, Lowndes CM, Alary M, 2000, Complementary hypothesis concerning the community sexually transmitted disease mass treatment puzzle in Rakai, Uganda, AIDS, Vol: 14, Pages: 2583-2592, ISSN: 0269-9370
BOILY M-C, POULIN R, MÂSSE B, 2000, Some Methodological Issues in the Study of Sexual Networks: From Model to Data to Model, Sexually Transmitted Diseases, Vol: 27, Pages: 558-571
Background: Mixing between sexual activity classes is an important determinant of sexually transmitted disease transmission. However, attempts to estimate sexual mixing patterns in the field remain limited partly because of practical and methodological difficulties.Goal: To evaluate and identify appropriate sampling schemes to estimate the mixing pattern between sexual activity classes from large population networks with one or more components.Study Design: The study is based on simulations of large population networks with various structural characteristics. A variety of snowball sampling schemes are applied to these networks and are evaluated by the quality of the mixing matrix estimates that they produce.Results and Conclusions: Unbiased estimation of mixing patterns (global assortativity, within-group mixing of the lowest activity classes, within-group mixing of the highest activity classes) from large population networks is possible with a snowball sampling design in which the initial sample of index cases is drawn from the general population, all partners of the index case are recruited, and only one generation of partners are traced (one cycle). Simulation techniques proved useful in addressing complex methodological issues in situations where analytic results are difficult to obtain.
POULIN R, Boily MC, Masse B, 2000, Dynamical systems to define centrality in social networks, Social Networks, Vol: 22, Pages: 187-220
In this paper, new measures of centrality that summarize the contact structure of social networks are proposed. The new measures use a cumulative nomination scheme based on the preliminary assumption that more central individuals will be nominated more often. Some of these measures are defined to characterize networks of different sizes and, by extension, networks made of many components. These new measures are applied to a network of 40 homosexuals with AIDS [Auerbach, D., Darrow, W., Jaffe, H., Curran, J., 1984. Cluster of cases of the acquired immune deficiency syndrome: patients linked by sexual contact. Am. J. Med. 76 (1984) 487–492; Klovdahl, A.S., 1985. Social networks and the spread of infectious diseases: the AIDS example. Soc. Sci. Med. 21 (1985) 1203–1216.], an illustrative multi-component network and a simulated network. They are compared to classical measures based on geodesics (closeness, eccentricity), to information-based centrality measures introduced by Stephenson and Zelen [Stephenson, K., Zelen, M., 1989. Rethinking centrality: methods and examples. Soc. Networks 11 (1989) 1–37.] and Altmann [Altmann, M., 1993. Reinterpreting network measures for models of disease transmission. Soc. Networks 15 (1993) 1–17.], and to the centrality measure of Bonacich [Bonacich, P., 1972. Factoring and weighting approaches to status scores and clique identification. J. Math. Sociol. 2 (1972) 113–120.]. The most basic of our measures is shown to be related to the Bonacich index of centrality for connected networks. The scaling law of the different centrality measures is examined by measuring simulated networks of various sizes. Measures based on the distribution of the components' size obey a simple proportional scaling law while those based on geodesics do not. Our new measures prove interesting because they consider all the possible paths, do not require intensive computer calculations, and can be used to compare networks of differen
Brisson M, Boily MC, Masse BR, et al., 1999, Highlights of the sexual activity of the heterosexual population in the province of Quebec, SEXUALLY TRANSMITTED INFECTIONS, Vol: 75, Pages: 296-299, ISSN: 1368-4973
Desai KN, Boily MC, Masse BR, et al., 1999, Simulation studies of phase III clinical trials to test the efficacy of a candidate HIV-1 vaccine, EPIDEMIOLOGY AND INFECTION, Vol: 123, Pages: 65-88, ISSN: 0950-2688
Boily MC, Masse BR, Desai K, et al., 1999, Some important issues in the planning of phase III HIV vaccine efficacy trials, VACCINE, Vol: 17, Pages: 989-1004, ISSN: 0264-410X
Boily MC, Masse BR, Desai K, et al., 1999, Some important issues in the planning of phase III HIV vaccine efficacy trials, Vaccine, Vol: 17:989-1004
Boily MC, Masse B, 1997, Mathematical models of disease transmission: A precious tool for the study of sexually transmitted diseases, CANADIAN JOURNAL OF PUBLIC HEALTH-REVUE CANADIENNE DE SANTE PUBLIQUE, Vol: 88, Pages: 255-265, ISSN: 0008-4263
Boily MC, Anderson RM, 1996, Human immunodeficiency virus transmission and the role of other sexually transmitted diseases - Measures of association and study design, SEXUALLY TRANSMITTED DISEASES, Vol: 23, Pages: 312-332, ISSN: 0148-5717
Boily MC, Brunham R, 1994, Erratum: The impact of HIV and other STDs on human populations: Are predictions possible? (Infectious Disease Clinics of North America (1993)), Infectious Disease Clinics of North America, Vol: 8, ISSN: 0891-5520
BOILY MC, BRUNHAM RC, 1993, THE IMPACT OF HIV AND OTHER STDS ON HUMAN-POPULATIONS - ARE PREDICTIONS POSSIBLE, INFECTIOUS DISEASE CLINICS OF NORTH AMERICA, Vol: 7, Pages: 771-792, ISSN: 0891-5520
Boily MC, 1993, The impact of HIV and other STDs on human populations. Are predictions possible?, Infect Dis Clin North Am., Vol: 4, Pages: 771-92
This article presents an overview of the use of mathematical models to study the demographic impact of STDs. Written for the nonmathematician, the article introduces the basic concepts of mathematical epidemiology for infectious diseases, such as the mass-action principle, the threshold density concept, and the basic reproductive rate. Described are the main features that characterize the epidemiology of STDs and those features that differentiate them from other directly transmitted diseases, such as measles, rubella, and others. Also presented are major findings concerning the importance of sexual behavior on the dynamics of STD transmission, and the numerical analysis of the demographic impact on gonococcal and HIV infections using a mathematical model. The epidemiology of these two STDs is explored, as well as how the growth rate of the population can influence the epidemiology of these STDs. Finally, the authors demonstrate how, under some circumstances, early treatment of gonorrhea can reduce the demographic impact of HIV in regions most affected by both diseases.
POTTS M, ANDERSON R, BOILY MC, 1991, SLOWING THE SPREAD OF HUMAN-IMMUNODEFICIENCY-VIRUS IN DEVELOPING-COUNTRIES, LANCET, Vol: 338, Pages: 608-613, ISSN: 0140-6736
ANDERSON RM, MAY RM, BOILY MC, et al., 1991, THE SPREAD OF HIV-1 IN AFRICA - SEXUAL CONTACT PATTERNS AND THE PREDICTED DEMOGRAPHIC-IMPACT OF AIDS, NATURE, Vol: 352, Pages: 581-589, ISSN: 0028-0836
BOILY MC, ANDERSON RM, 1991, SEXUAL CONTACT PATTERNS BETWEEN MEN AND WOMEN AND THE SPREAD OF HIV-1 IN URBAN CENTERS IN AFRICA, IMA JOURNAL OF MATHEMATICS APPLIED IN MEDICINE AND BIOLOGY, Vol: 8, Pages: 221-247, ISSN: 0265-0746
ANDERSON RM, NG TW, BOILY MC, et al., 1989, THE INFLUENCE OF DIFFERENT SEXUAL-CONTACT PATTERNS BETWEEN AGE CLASSES ON THE PREDICTED DEMOGRAPHIC-IMPACT OF AIDS IN DEVELOPING-COUNTRIES, ANNALS OF THE NEW YORK ACADEMY OF SCIENCES, Vol: 569, Pages: 240-274, ISSN: 0077-8923
ANDERSON RM, NG TW, BOILY MC, et al., 1989, THE INFLUENCE OF DIFFERENT SEXUAL-CONTACT PATTERNS BETWEEN AGE CLASSES ON THE PREDICTED DEMOGRAPHIC-IMPACT OF AIDS IN DEVELOPING-COUNTRIES, CONF ON BIOMEDICAL SCIENCE AND THE THIRD WORLD : UNDER THE VOLCANO, Publisher: NEW YORK ACAD SCIENCES, Pages: 240-274
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