This paper reports qualitative findings from a study examining the context of injection drug use ... more This paper reports qualitative findings from a study examining the context of injection drug use (IDU) and HIV/AIDS in Victoria, Canada. Objectives were to determine behaviours and situations that place IDUs at risk for blood-borne diseases and to use this information to ...
To plan and implement services to persons who inject drugs (PWID), knowing their number is essent... more To plan and implement services to persons who inject drugs (PWID), knowing their number is essential. For the island of Montréal, Canada, the only estimate, of 11,700 PWID, was obtained in 1996 through a capture-recapture method. Thirteen years later, this study was undertaken to produce a new estimate. PWID were defined as individuals aged 14-65 years, having injected recently and living on the island of Montréal. The study period was 07/01/2009 to 06/30/2010. An estimate was produced using a six-source capture-recapture log-linear regression method. The data sources were two epidemiological studies and four drug dependence treatment centres. Model selection was conducted in two steps, the first focusing on interactions between sources and the second, on age group and gender as covariates and as modulators of interactions. A total of 1480 PWID were identified in the six capture sources. They corresponded to 1132 different individuals. Based on the best-fitting model, which included...
Failure to understand the risk of false-negative HIV test results during the window period result... more Failure to understand the risk of false-negative HIV test results during the window period results in anxiety. Patients typically want accurate test results as soon as possible while clinicians prefer to wait until the probability of a false-negative is virtually nil. This review summarizes the median window periods for third-generation antibody and fourth-generation HIV tests and provides the probability of a false-negative result for various days post-exposure. Data were extracted from published seroconversion panels. A 10-day eclipse period was used to estimate days from infection to first detection of HIV RNA. Median (interquartile range) days to seroconversion were calculated and probabilities of a false-negative result at various time periods post-exposure are reported. The median (interquartile range) window period for third-generation tests was 22 days (19-25) and 18 days (16-24) for fourth-generation tests. The probability of a false-negative result is 0.01 at 80 days' ...
Many people who are HIV positive are unaware of their infection status. Estimation of the number ... more Many people who are HIV positive are unaware of their infection status. Estimation of the number of people with undiagnosed HIV within a country or region is vital for understanding future need for treatment and for motivating testing programs. We review the available estimation approaches which are in current use. They can be broadly classified into those based on prevalence surveys and those based on reported HIV and AIDS cases. Estimation based on prevalence data requires data from regular prevalence surveys in different population groups together with estimates of the size of these groups. The recommended minimal case reporting data needed to estimate the number of patients with undiagnosed HIV are HIV diagnoses, including CD4 count at diagnosis and whether there has been an AIDS diagnosis in the 3 months before or after HIV diagnosis, and data on deaths in people with HIV. We would encourage all countries to implement several methods that will help develop our understanding of strengths and weaknesses of the various methods.
Hepatitis C virus (HCV) infection has a high likelihood of becoming chronic and lead to a range o... more Hepatitis C virus (HCV) infection has a high likelihood of becoming chronic and lead to a range of conditions with poor health outcomes. Identifying birth groups highly affected by HCV infection may better focus public health interventions and ensure their cost-effectiveness. Our analysis focused on studying the association of the birth year and reporting period with rates of cases of HCV infection reported in Canada over a 20-year period. Laboratory-confirmed acute or chronic HCV cases with information on sex, age and year of report from 6 provinces and territories that reported line-listed data to the Canadian Notifiable Diseases Surveillance System from 1991 to 2010 were used. Sex-specific infection rates for 5-year birth groups born between 1921 and 1990 were calculated. Rates of HCV infection were log-logit transformed and underwent mean polish analysis and panel linear regression. Rate ratios of HCV infection in the 5-year age groups and their 95% confidence intervals were cal...
North American Journal of Fisheries Management, 1983
Pacific ocean perch (Sebastes alutus) have undergone considerable over-exploitation in Queen Char... more Pacific ocean perch (Sebastes alutus) have undergone considerable over-exploitation in Queen Charlotte Sound, British Columbia, largely as a result of excessive removals by foreign fleets in the 1965-1974 period. A new catch-at-age model is used to reconstruct the history of this stock through simultaneous analysis for all cohorts present in the time series of catch data. The reconstruction extends from
JAIDS Journal of Acquired Immune Deficiency Syndromes, 2006
Published results on primary or transmitted HIV drug resistance may be biased because they have b... more Published results on primary or transmitted HIV drug resistance may be biased because they have been largely derived from specific cohort studies or higher risk individuals who present symptomatically. Here, we present results from a representative population-based study of newly diagnosed cases of HIV in Canada and compare the prevalence of transmitted drug resistance between recent and established infections. Available archived sera taken for the purpose of diagnostic HIV testing from all treatment-naive HIV-positive individuals who were newly diagnosed between 2000 and 2001 were tested for recency of infection, HIV-1 subtype, and mutations conferring reduced susceptibility to reverse transcriptase inhibitors and protease inhibitors (PIs). Recent infections were identified using the Organon Teknika Vironostika HIV-1-LS assay. After full-length sequencing of the pol gene, drug resistance mutations were identified using the 2004 International AIDS Society-USA mutations panel. Differences in drug resistance profiles between recent and prevalent infections were examined using the chi test and the Fisher exact test. The variables examined included gender, age at diagnosis, year of diagnosis, exposure category, ethnicity, and HIV-1 subtype. Among the study population, 8.1% had genotypic evidence of transmitted drug resistance: 4.1% against nucleoside reverse transcriptase inhibitors, 1.4% against nonnucleoside reverse transcriptase inhibitors, 1.5% against PIs, and 1% against > or =2 classes of drugs. A higher proportion of recent infections had genotypic evidence of transmitted drug resistance when compared with established infections (12.2% vs. 6.1%, respectively; P = 0.005). Transmitted drug resistance was identified mainly among recently infected Caucasian men who have sex with men but it was not limited to this group. Compared with the year 2000, a higher proportion of recently infected individuals with resistance-conferring mutations were diagnosed during the year 2001 (66.7% vs. 46.6%). In Canada, transmitted drug resistance is occurring within all 3 drug classes and across different population groups. The results suggest that the prevalence rates may be higher among recent versus established infections. Given the public health implications of transmitting drug-resistant HIV, it is important to continue population-based drug resistance surveillance to guide optimum prevention and treatment of HIV infection.
JAIDS Journal of Acquired Immune Deficiency Syndromes, 2009
During a routine surveillance round, an extremely high prevalence of 51.3% was found among inject... more During a routine surveillance round, an extremely high prevalence of 51.3% was found among injecting drug users (IDUs) in Sargodha, a small town in Pakistan. This sharp increase of HIV among this group warranted an urgent need to explore the factors leading toward this explosion of HIV infection among IDUs at this very location to direct the policy makers in designing preventive activities, especially in the context of HIV prevention. In 2007, 400 current IDUs were recruited through multistage cluster sampling based on mapping studies. Participants provided dried blood spot samples for HIV testing and completed a questionnaire on demographic characteristics and sexual/drug injecting behaviors. Logistic regression was used to examine the independent association of multiple variables with HIV infection. Of the 400 IDUs tested, 205 (51.3%) were HIV positive confirmed through enzyme-linked immunosorbent assay and Western blot. In multivariate analysis, geographical location of IDUs [adjusted odds ratio (aOR) 2.4 for IDUs located in the northern zone vs southern zone, 95% confidence interval (CI) 1.5 to 3.7], injected in groups (aOR 1.8, 95% CI 1.1 to 3.1), and sharing injecting paraphernalia with other IDUs (aOR 1.5, 95% CI 1.0 to 2.4) were strong correlates of HIV infection. Effective outreach programs need to be developed to provide a comprehensive package of HIV prevention services to IDUs not reached by existing services, entry into drug abuse treatment and medical care needs to be facilitated, and essential legal and social services need to be provided with community participation.
... 1British Columbia Centre for Disease Control, Vancouver, 2Department of Medicine, University ... more ... 1British Columbia Centre for Disease Control, Vancouver, 2Department of Medicine, University of British Columbia, Vancouver, 3British Columbia Centre for Excellence in HIV/AIDS, Vancouver, 4Department of Health ... Social determinants are powerful predictors of health22. ...
We examined factors associated with the subsequent development of AIDS-related Kaposi's s... more We examined factors associated with the subsequent development of AIDS-related Kaposi's sarcoma in a cohort of 353 homosexual men infected with human immunodeficiency virus (HIV). Cumulative incidence curves for the development of Kaposi's sarcoma and opportunistic infection were stratified over a wide range of variables at enrollment, including those related to demographics, sexual behavior, illicit drug use, and medical history. We found no strong associations between any of these variables and the development of opportunistic infection, but two were related to Kaposi's sarcoma: use of nitrite inhalants (relative risk, 2.3; 95% confidence interval, 1.0-5.0) and high numbers of sexual contacts during the period 1978-1982 in the AIDS epidemic centers of San Francisco, Los Angeles, and/or New York (relative risk, 3.5; 95% confidence interval, 1.6-7.6). The latter variables remained independently associated with risk of Kaposi's sarcoma even after multivariate adjustment for a number of classical HIV risk factors. These results are consistent with the hypothesis that Kaposi's sarcoma is caused by a sexually transmitted cofactor that has remained more prevalent in the original epidemic centers. The effect of nitrites could be due to an independent biological mechanism or to enhancement of transmission of the cofactor.
Canadian Journal of Fisheries and Aquatic Sciences, 1982
We present a general theory for analyzing catch at age data for a fishery. This theory seems to b... more We present a general theory for analyzing catch at age data for a fishery. This theory seems to be the first to address itself properly to the stochastic nature of the errors in the observed catch at age data. The model developed is very flexible and accommodates itself easily to ...
ABSTRACT This paper introduces Monte Carlo *-Minimax Search (MCMS), a Monte-Carlo search algorith... more ABSTRACT This paper introduces Monte Carlo *-Minimax Search (MCMS), a Monte-Carlo search algorithm for finite, turned based, stochastic, two-player, zero-sum games of perfect information. Through a combination of sparse sam-pling and classical pruning techniques, MCMS allows deep plans to be con-structed. Unlike other popular tree search techniques, MCMS is suitable for densely stochastic games, i.e., games where one would never expect to sample the same state twice. We give a basis for the theoretical properties of the al-gorithm and evaluate its performance in three games: Pig (Pig Out), EinStein Würfelt Nicht!, and Can't Stop.
Many people who are HIV positive are unaware of their infection status. Estimation of the number ... more Many people who are HIV positive are unaware of their infection status. Estimation of the number of people with undiagnosed HIV within a country or region is vital for understanding future need for treatment and for motivating testing programs. We review the available estimation approaches which are in current use. They can be broadly classified into those based on prevalence surveys and those based on reported HIV and AIDS cases. Estimation based on prevalence data requires data from regular prevalence surveys in different population groups together with estimates of the size of these groups. The recommended minimal case reporting data needed to estimate the number of patients with undiagnosed HIV are HIV diagnoses, including CD4 count at diagnosis and whether there has been an AIDS diagnosis in the 3 months before or after HIV diagnosis, and data on deaths in people with HIV. We would encourage all countries to implement several methods that will help develop our understanding of strengths and weaknesses of the various methods.
This paper reports qualitative findings from a study examining the context of injection drug use ... more This paper reports qualitative findings from a study examining the context of injection drug use (IDU) and HIV/AIDS in Victoria, Canada. Objectives were to determine behaviours and situations that place IDUs at risk for blood-borne diseases and to use this information to ...
To plan and implement services to persons who inject drugs (PWID), knowing their number is essent... more To plan and implement services to persons who inject drugs (PWID), knowing their number is essential. For the island of Montréal, Canada, the only estimate, of 11,700 PWID, was obtained in 1996 through a capture-recapture method. Thirteen years later, this study was undertaken to produce a new estimate. PWID were defined as individuals aged 14-65 years, having injected recently and living on the island of Montréal. The study period was 07/01/2009 to 06/30/2010. An estimate was produced using a six-source capture-recapture log-linear regression method. The data sources were two epidemiological studies and four drug dependence treatment centres. Model selection was conducted in two steps, the first focusing on interactions between sources and the second, on age group and gender as covariates and as modulators of interactions. A total of 1480 PWID were identified in the six capture sources. They corresponded to 1132 different individuals. Based on the best-fitting model, which included...
Failure to understand the risk of false-negative HIV test results during the window period result... more Failure to understand the risk of false-negative HIV test results during the window period results in anxiety. Patients typically want accurate test results as soon as possible while clinicians prefer to wait until the probability of a false-negative is virtually nil. This review summarizes the median window periods for third-generation antibody and fourth-generation HIV tests and provides the probability of a false-negative result for various days post-exposure. Data were extracted from published seroconversion panels. A 10-day eclipse period was used to estimate days from infection to first detection of HIV RNA. Median (interquartile range) days to seroconversion were calculated and probabilities of a false-negative result at various time periods post-exposure are reported. The median (interquartile range) window period for third-generation tests was 22 days (19-25) and 18 days (16-24) for fourth-generation tests. The probability of a false-negative result is 0.01 at 80 days' ...
Many people who are HIV positive are unaware of their infection status. Estimation of the number ... more Many people who are HIV positive are unaware of their infection status. Estimation of the number of people with undiagnosed HIV within a country or region is vital for understanding future need for treatment and for motivating testing programs. We review the available estimation approaches which are in current use. They can be broadly classified into those based on prevalence surveys and those based on reported HIV and AIDS cases. Estimation based on prevalence data requires data from regular prevalence surveys in different population groups together with estimates of the size of these groups. The recommended minimal case reporting data needed to estimate the number of patients with undiagnosed HIV are HIV diagnoses, including CD4 count at diagnosis and whether there has been an AIDS diagnosis in the 3 months before or after HIV diagnosis, and data on deaths in people with HIV. We would encourage all countries to implement several methods that will help develop our understanding of strengths and weaknesses of the various methods.
Hepatitis C virus (HCV) infection has a high likelihood of becoming chronic and lead to a range o... more Hepatitis C virus (HCV) infection has a high likelihood of becoming chronic and lead to a range of conditions with poor health outcomes. Identifying birth groups highly affected by HCV infection may better focus public health interventions and ensure their cost-effectiveness. Our analysis focused on studying the association of the birth year and reporting period with rates of cases of HCV infection reported in Canada over a 20-year period. Laboratory-confirmed acute or chronic HCV cases with information on sex, age and year of report from 6 provinces and territories that reported line-listed data to the Canadian Notifiable Diseases Surveillance System from 1991 to 2010 were used. Sex-specific infection rates for 5-year birth groups born between 1921 and 1990 were calculated. Rates of HCV infection were log-logit transformed and underwent mean polish analysis and panel linear regression. Rate ratios of HCV infection in the 5-year age groups and their 95% confidence intervals were cal...
North American Journal of Fisheries Management, 1983
Pacific ocean perch (Sebastes alutus) have undergone considerable over-exploitation in Queen Char... more Pacific ocean perch (Sebastes alutus) have undergone considerable over-exploitation in Queen Charlotte Sound, British Columbia, largely as a result of excessive removals by foreign fleets in the 1965-1974 period. A new catch-at-age model is used to reconstruct the history of this stock through simultaneous analysis for all cohorts present in the time series of catch data. The reconstruction extends from
JAIDS Journal of Acquired Immune Deficiency Syndromes, 2006
Published results on primary or transmitted HIV drug resistance may be biased because they have b... more Published results on primary or transmitted HIV drug resistance may be biased because they have been largely derived from specific cohort studies or higher risk individuals who present symptomatically. Here, we present results from a representative population-based study of newly diagnosed cases of HIV in Canada and compare the prevalence of transmitted drug resistance between recent and established infections. Available archived sera taken for the purpose of diagnostic HIV testing from all treatment-naive HIV-positive individuals who were newly diagnosed between 2000 and 2001 were tested for recency of infection, HIV-1 subtype, and mutations conferring reduced susceptibility to reverse transcriptase inhibitors and protease inhibitors (PIs). Recent infections were identified using the Organon Teknika Vironostika HIV-1-LS assay. After full-length sequencing of the pol gene, drug resistance mutations were identified using the 2004 International AIDS Society-USA mutations panel. Differences in drug resistance profiles between recent and prevalent infections were examined using the chi test and the Fisher exact test. The variables examined included gender, age at diagnosis, year of diagnosis, exposure category, ethnicity, and HIV-1 subtype. Among the study population, 8.1% had genotypic evidence of transmitted drug resistance: 4.1% against nucleoside reverse transcriptase inhibitors, 1.4% against nonnucleoside reverse transcriptase inhibitors, 1.5% against PIs, and 1% against > or =2 classes of drugs. A higher proportion of recent infections had genotypic evidence of transmitted drug resistance when compared with established infections (12.2% vs. 6.1%, respectively; P = 0.005). Transmitted drug resistance was identified mainly among recently infected Caucasian men who have sex with men but it was not limited to this group. Compared with the year 2000, a higher proportion of recently infected individuals with resistance-conferring mutations were diagnosed during the year 2001 (66.7% vs. 46.6%). In Canada, transmitted drug resistance is occurring within all 3 drug classes and across different population groups. The results suggest that the prevalence rates may be higher among recent versus established infections. Given the public health implications of transmitting drug-resistant HIV, it is important to continue population-based drug resistance surveillance to guide optimum prevention and treatment of HIV infection.
JAIDS Journal of Acquired Immune Deficiency Syndromes, 2009
During a routine surveillance round, an extremely high prevalence of 51.3% was found among inject... more During a routine surveillance round, an extremely high prevalence of 51.3% was found among injecting drug users (IDUs) in Sargodha, a small town in Pakistan. This sharp increase of HIV among this group warranted an urgent need to explore the factors leading toward this explosion of HIV infection among IDUs at this very location to direct the policy makers in designing preventive activities, especially in the context of HIV prevention. In 2007, 400 current IDUs were recruited through multistage cluster sampling based on mapping studies. Participants provided dried blood spot samples for HIV testing and completed a questionnaire on demographic characteristics and sexual/drug injecting behaviors. Logistic regression was used to examine the independent association of multiple variables with HIV infection. Of the 400 IDUs tested, 205 (51.3%) were HIV positive confirmed through enzyme-linked immunosorbent assay and Western blot. In multivariate analysis, geographical location of IDUs [adjusted odds ratio (aOR) 2.4 for IDUs located in the northern zone vs southern zone, 95% confidence interval (CI) 1.5 to 3.7], injected in groups (aOR 1.8, 95% CI 1.1 to 3.1), and sharing injecting paraphernalia with other IDUs (aOR 1.5, 95% CI 1.0 to 2.4) were strong correlates of HIV infection. Effective outreach programs need to be developed to provide a comprehensive package of HIV prevention services to IDUs not reached by existing services, entry into drug abuse treatment and medical care needs to be facilitated, and essential legal and social services need to be provided with community participation.
... 1British Columbia Centre for Disease Control, Vancouver, 2Department of Medicine, University ... more ... 1British Columbia Centre for Disease Control, Vancouver, 2Department of Medicine, University of British Columbia, Vancouver, 3British Columbia Centre for Excellence in HIV/AIDS, Vancouver, 4Department of Health ... Social determinants are powerful predictors of health22. ...
We examined factors associated with the subsequent development of AIDS-related Kaposi's s... more We examined factors associated with the subsequent development of AIDS-related Kaposi's sarcoma in a cohort of 353 homosexual men infected with human immunodeficiency virus (HIV). Cumulative incidence curves for the development of Kaposi's sarcoma and opportunistic infection were stratified over a wide range of variables at enrollment, including those related to demographics, sexual behavior, illicit drug use, and medical history. We found no strong associations between any of these variables and the development of opportunistic infection, but two were related to Kaposi's sarcoma: use of nitrite inhalants (relative risk, 2.3; 95% confidence interval, 1.0-5.0) and high numbers of sexual contacts during the period 1978-1982 in the AIDS epidemic centers of San Francisco, Los Angeles, and/or New York (relative risk, 3.5; 95% confidence interval, 1.6-7.6). The latter variables remained independently associated with risk of Kaposi's sarcoma even after multivariate adjustment for a number of classical HIV risk factors. These results are consistent with the hypothesis that Kaposi's sarcoma is caused by a sexually transmitted cofactor that has remained more prevalent in the original epidemic centers. The effect of nitrites could be due to an independent biological mechanism or to enhancement of transmission of the cofactor.
Canadian Journal of Fisheries and Aquatic Sciences, 1982
We present a general theory for analyzing catch at age data for a fishery. This theory seems to b... more We present a general theory for analyzing catch at age data for a fishery. This theory seems to be the first to address itself properly to the stochastic nature of the errors in the observed catch at age data. The model developed is very flexible and accommodates itself easily to ...
ABSTRACT This paper introduces Monte Carlo *-Minimax Search (MCMS), a Monte-Carlo search algorith... more ABSTRACT This paper introduces Monte Carlo *-Minimax Search (MCMS), a Monte-Carlo search algorithm for finite, turned based, stochastic, two-player, zero-sum games of perfect information. Through a combination of sparse sam-pling and classical pruning techniques, MCMS allows deep plans to be con-structed. Unlike other popular tree search techniques, MCMS is suitable for densely stochastic games, i.e., games where one would never expect to sample the same state twice. We give a basis for the theoretical properties of the al-gorithm and evaluate its performance in three games: Pig (Pig Out), EinStein Würfelt Nicht!, and Can't Stop.
Many people who are HIV positive are unaware of their infection status. Estimation of the number ... more Many people who are HIV positive are unaware of their infection status. Estimation of the number of people with undiagnosed HIV within a country or region is vital for understanding future need for treatment and for motivating testing programs. We review the available estimation approaches which are in current use. They can be broadly classified into those based on prevalence surveys and those based on reported HIV and AIDS cases. Estimation based on prevalence data requires data from regular prevalence surveys in different population groups together with estimates of the size of these groups. The recommended minimal case reporting data needed to estimate the number of patients with undiagnosed HIV are HIV diagnoses, including CD4 count at diagnosis and whether there has been an AIDS diagnosis in the 3 months before or after HIV diagnosis, and data on deaths in people with HIV. We would encourage all countries to implement several methods that will help develop our understanding of strengths and weaknesses of the various methods.
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