Chris P. Archibald

Reemergence of the HIV epidemic among men who have sex with men in North America, Western Europe, and Australia, 1996-2005.

PURPOSE To describe and contextualize changes in rates of human immunodeficiency virus (HIV) notifications in men who have sex with men (MSM) in eight countries (Australia, Canada, France, Germany, Netherlands, Spain, United Kingdom, and United States) from 1996-2005. METHODS We analyzed trends in HIV notification rates from 1996-2000 and 2000-2005 by generalized linear regression and estimated annual percentage change (EAPC) in rates of HIV notifications. To interpret trends, we visually examined graphs of primary and secondary syphilis reports among MSM and the prevalence of recent HIV testing. RESULTS The rate of HIV notifications among MSM declined 5.2% per year (95% confidence interval [CI]: -5.8%, -4.7%) from 1996-2000, and increased 3.3% per year (95% CI: +2.9%,+3.7%) from 2000-2005. During the period of increasing HIV diagnoses, increases in primary and secondary syphilis diagnoses occurred among MSM, but recent HIV testing among MSM did not seem to increase. CONCLUSIONS After declining in the second half of the 1990s, HIV notification rates for MSM increased beginning in 2000. Increased HIV notifications in MSM are not wholly explained by changes in HIV testing. Urgent efforts are required to develop effective HIV prevention interventions for MSM, and implement them broadly in these countries.

Determinants of HIV seroconversion in drug users during a period of rising prevalence in Vancouver

To identify determinants of HIV seroconversion among injection drug users (IDUs) during a period of rising prevalence, a case-control investigation was conducted. Cases were IDUs with a new positive test after 1 January 1994, and a negative test within the prior 18 months. Controls required 2 negative tests during the same period. Subjects completed a questionnaire on demographic, psychosocial, and behavioural factors. Eighty-nine cases and 192 controls were similar with respect to gender, age, ethnicity and inter-test interval. Multivariate analyses of events during the inter-test interval showed borrowing syringes (adj. OR=2.96; P 0.006), unstable housing (adj. OR=2.01; P =0.03) and injecting 4 times daily (adj. OR=1.71; P =0.06) to be independently associated with seroconversion. Protective associations were demonstrated for sex with opposite gender (adj. OR=0.36; P =0.001) and tetrahydrocannabinol use (adj. OR=0.41; P =0.001). There is a need to evaluate programmes dealing with addiction, housing and the social underpinnings of risk behaviours in this population. <

A population-based approach to determine the prevalence of transmitted drug-resistant HIV among recent versus established HIV infections: results from the Canadian HIV strain and drug resistance surveillance program.

Objectives: 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. Methods: 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 &khgr;2 test and the Fisher exact test. The variables examined included gender, age at diagnosis, year of diagnosis, exposure category, ethnicity, and HIV-1 subtype. Results: 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 ≥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%). Conclusions: 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.

Factors associated with frequent needle exchange program attendance in injection drug users in Vancouver, Canada

The objective of this study was to identify factors associated with frequent needle exchange program (NEP) attendance by injection drug users (IDUs) in Vancouver, Canada. Data were examined from a case control study of recent HIV infection. IDUs with documented HIV seroconversion after January 1, 1994 (n = 89) and seronegative controls with two documented HIV-negative test results in the same period (n = 192) were asked about demographic and social information, drug injection and sexual behavior, and NEP attendance. Logistic regression was used to examine the effect of multiple variables on NEP attendance while adjusting for HIV status and other potential confounders. Frequent (> 1 time/week) versus nonfrequent (< or = 1 time/week) NEP attenders did not differ with respect to gender, age, ethnicity, education, or HIV serostatus. For men, multivariate analysis showed that frequent cocaine injection was the only variable independently associated with NEP attendance (adjusted odds ratio [AOR] = 3.9; 95% confidence interval [CI] = 1.8-8.3); for women, independently associated variables were frequency of any drug injection (AOR = 5.5; 95% CI = 1.7-17), shooting gallery attendance (AOR = 11.5; 95% CI = 2.2-66), and having a nonlegal source of income (AOR = 3.4; 95% CI = 1.0-12). Borrowing used needles was associated with frequent NEP attendance in the univariate analysis. The NEP in Vancouver attracts IDUs who are frequent injectors (especially men using cocaine) and who have high-risk behaviors or an unstable lifestyle. This finding reinforces the role of NEPs as potential focal points for intervention in this hard-to-reach population.

Estimating the size of hard-to-reach populations: a novel method using HIV testing data compared to other methods.

Objective: To estimate population size of hard-to-reach groups such as injecting drug users and men who have sex with men. Design: Several different methods were used to estimate the size of these populations in Canadas three largest cities (Toronto, Montreal and Vancouver). Methods: A novel method (referred to as the indirect method) was developed for use in Toronto and Vancouver that combines HIV serodiagnostic information with data on HIV testing behavior. Population size estimates were obtained by dividing the number of injecting drug users or men who have sex with men recorded in HIV serodiagnostic databases in a given year by the proportion of the corresponding group that reported being tested in a 1-year period. Results of this method were compared with four other methods: (1) population surveys; (2) capture-recapture (for injecting drug users only); (3) a modified Delphi technique; and (4) a method based on the proportion of never-married men aged 45 and over (for men who have sex with men only). Only these other methods were used in Montreal. Results: The survey method gave the lowest estimates which are best viewed as minimum estimates given the relative inability of surveys to access these populations and the reluctance of participants to admit to sensitive behaviors. The indirect method produced results more closely comparable with those obtained by other methods, but they are probably slight overestimates, at least for injecting drug users, due to possible underestimation of the proportion tested for HIV. Point estimates using the indirect method were 17 700 and 17 500 for injecting drug users in Toronto and Vancouver, respectively, and 39 100 and 15 900 for men who have sex with men. In Toronto, results for the other methods ranged from 12 300-13 360 for injecting drug users and 18 800-35 000 for men who have sex with men. For Vancouver, these ranges were 6400-11 670 and 7000-26 500, respectively. In Montreal, ranges were 4300-12 500 for injecting drug users and 18 500-40 000 for men who have sex with men. Conclusions: This novel method provides estimates of population size of hard-to-reach groups such as injecting drug users and men who have sex with men that are comparable with results derived by other methods. These estimates may be useful for the purposes of planning, implementing and evaluating prevention and care services, especially when they are combined with the results of other estimation methods to improve the degree of confidence in the resulting estimates.

A qualitative investigation into an HIV outbreak among injection drug users in Vancouver, British Columbia

The proportion of injection drug users (IDUs) testing positive for Human Immunodeficiency Virus (HIV) in British Columbia has increased from 3 to 7% since January 1993 (Patrick et al., 1997). We conducted a qualitative study as a first step in a case control investigation aimed at identifying risk factors associated with HIV seroconversion. Sixteen subjects participated in in-depth interviews which were transcribed and analysed using grounded theory methods. Three dominant themes emerged: Addiction, Prevention, and Social Determinants. The results suggest that prevention efforts such as the availability of clean needles and condoms are not adequate to combat the complex social determinants of addiction--be they causal or consequential--which in turn contribute to unsafe injection practices.

Evidence for a sexually transmitted cofactor for AIDS-related Kaposi's sarcoma in a cohort of homosexual men.

We examined factors associated with the subsequent development of AIDS-related Kaposis sarcoma in a cohort of 353 homosexual men infected with human immunodeficiency virus (HIV). Cumulative incidence curves for the development of Kaposis 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 Kaposis 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 Kaposis sarcoma even after multivariate adjustment for a number of classical HIV risk factors. These results are consistent with the hypothesis that Kaposis 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. (Epidemiology 1992;3:203-209)

Longitudinal phylogenetic surveillance identifies distinct patterns of cluster dynamics.

Objective:Through the application of simple, accessible, molecular epidemiology tools, we aimed to resolve the phylogenetic relationships that best predicted patterns of cluster growth using longitudinal population level drug resistance genotype data. Methods:Analysis was performed on 971 specimens from drug naïve, first time HIV positive subjects collected in British Columbia between 2002 and 2005. A 1240bp fragment of the pol gene was amplified and sequenced with relationships among subtype B sequences inferred using Neighbour-Joining analysis. Apparent clusters of infections having both a mean within group distance <0.031 and bootstrap value >80% were systematically identified. The entire 2002-2005 dataset was then re-analyze to evaluate the relationship of subsequent infections to those identified in 2002. BED testing was used to identify recent infections (<156 days). Results:Among the 2002 infections, 136 of 300 sequences sorted into 52 clusters ranging in size from 2 to 9 members. Aboriginal ethnicity and intravenous drug use were correlated, and both were linked to cluster membership in 2002. Although cluster growth between 2002 and 2005 was correlated with the size of the original cluster, more related infections were found in clusters seeded from nonclustered infections. Finally, all large growth clusters were seeded from infections that were much more likely to be recent. Conclusions:This population level phylogenetic analysis suggests that a greater increase in cluster size is associated with recently infected individuals, which may represent the leading edge of the epidemic. The most impressive increase in cluster size is seen originating from initially nonclustered infections. In contrast, smaller existing clusters likely describe historical patterns of transmission and do not substantially contribute to the ongoing epidemic. Application of this method for cross-sectional analysis of existing sequences from defined geographic regions may be useful in predicting trends in HIV transmission.

Factors associated with HIV testing among Canadians: results of a population-based survey

Summary: The purpose of this study was to examine the HIV-testing behaviour of Canadians aged 15 years and older. Questions on HIV testing were asked as part of a Canada-wide random digit dialling telephone survey conducted in December 1995 to January 1996 on health practices and attitudes toward health care in Canada ( n =3123). Including blood donation and insurance testing, 40.4% of men and 30.4% of women had been tested for HIV. Excluding blood donation and life-insurance testing (voluntary testing), 17.8% of men and 15.6% of women had been tested. In multivariate analyses, factors independently associated with voluntary testing among men were: having had sex with a man (OR=16.8), injection drug use (OR=5.8), having had a partner at high risk (OR=2.5), having received blood or clotting factor (OR=2.3), being younger than 45 years of age (OR=1.8), living in a city of over one million (OR=1.7), and making less than

Genomic Epidemiology and Molecular Resistance Mechanisms of Azithromycin-Resistant Neisseria gonorrhoeae in Canada from 1997 to 2014

30,000 a year (OR=1.6). For women, factors independently associated with voluntary testing were having received blood or clotting factor (OR=3.9), having had a high-risk partner (OR= 3.5), being younger than 45 years of age (OR=2.4), having had sex with a man (OR=2.3), and being unattached (OR=2.0). Results indicated that those at risk are more likely to be tested. It is of concern, however, that many of those reporting risk factors have not been tested. A better understanding of HIV testing behaviour is needed to improve the planning and evaluation of prevention and counselling services.