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INFECTIOUS DISEASE SURVEILLANCE
in Canadian Federal Penitentiaries 2005-2006

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Executive Summary

Background

In the mid-1990’s, response to a suspected outbreak of tuberculosis in several federal facilities led to an ongoing collaboration between the Public Health Agency of Canada (PHAC) (then Health Canada) and Correctional Service Canada (CSC), Health Services Sector (then Health Services Branch). In 2003, CSC and PHAC formalized this collaboration and signed a Memorandum of Understanding (MOU) in order to enhance infectious disease prevention and control among inmates and staff in federal correctional facilities. This agreement includes the provision of epidemiological and data management services including surveillance, and since 2003 PHAC personnel have been providing expert technical and medical advice to CSC on a wide variety of infectious disease and public health issues.

Two separate technical surveillance systems were in place between 2005 and 2006 to capture surveillance data. The CSC Infectious Disease Surveillance System (IDSS) is an aggregate register of monthly serology screening tests and case reports of human immunodeficiency virus (HIV), hepatitis C (HCV), hepatitis A (HAV), hepatitis B (HBV), tuberculosis (TB), and sexually transmitted infections (STI). The Web-enabled Infectious Disease Surveillance System (Web-IDSS) is a normalized electronic database containing enhanced, line-listed data on tuberculosis (TB) and bloodborne and sexually transmitted infections (BBSTI). Tuberculosis screening for staff is conducted by the Public Health and Occupational Safety Program (PHOSP) of Health Canada and is stored and analyzed by PHAC.

This report presents the combined surveillance data for 2005 – 2006 on selected infectious diseases for CSC. This builds on previously published surveillance results for 2000-2001 (CSC, 2003) and 2002-2004 (CSC, 2008), and on previously published reports on tuberculosis for 1998 (CSC, 2001) and 1999-2001 (CSC, 2005).

This is the first report in which Web-IDSS data are presented. The information from the enhanced screening include previous testing and results, risk-history information, tests requested and laboratory results, and the ability to link multiple tests for an individual across time. However, as 2005-2006 represent ramp-up and implementation phases, these data are used to supplement and enhance the findings from the aggregate surveillance system. Therefore, the IDSS data are still considered the “gold standard” with respect to providing best-estimate data for testing and prevalence estimates.

Results

More than half of new admissions  to a CSC correctional facility accepted a screening blood test for HIV in 2005 and 2006. In each of these years, 7 new admissions were newly diagnosed for HIV, or 2.9 and 2.6 newly diagnosed HIV cases per 1,000 tests respectively. The vast majority of HIV infections among inmates were known on admission; for example, in 2006, 155 of 162 (96%) HIV cases were known to be positive on admission. The year-end point-prevalence estimate for HIV infection was 1.67% in 2005 (N=204) and 1.64% in 2006 (N=218). Women had higher rates of HIV infection compared to men; in 2006 the year-end HIV prevalence rates for women was 4.49% compared to 1.54% for men. The number of known HIV positive inmates released to the community was 175 in 2005 and 193 in 2006. Enhanced surveillance data from 2005 and 2006 indicate that among inmates who had a baseline negative HIV test and a follow-up test while incarcerated, no new HIV infections were detected.

About half of all new admissions accepted a screening blood test for HCV in 2005 and 2006. Of these, there were 178 newly diagnosed HCV infections in 2005 and 193 in 2006. This translates to a diagnostic yield of 75.2 newly diagnosed HCV infections per 1,000 tests in 2005 and 76.9 in 2006. The vast majority of HCV infections among inmates were known on admission; for example, in 2006, 1,165 of 1,358 (86%) HCV cases were known to be positive on admission. The point-prevalence estimate for HCV infection was 29.3% in 2005 (N=3,581) and 27.6% in 2006 (N=3,661). Women had higher rates of HCV infection compared to men; in 2006 the year-end HCV prevalence rate for women was 36.0% compared to 27.3% for men. The number of known HCV positive inmates released to the community was 2,065 in 2005 and 2,183 in 2006. Enhanced surveillance data from 2005-2006 indicate that of the inmates who tested negative on admission and had a repeat HCV test, an estimated 31 per 1,000 per year subsequently test positive during incarceration. However, attribution of infection to risk inside CSC is limited due to the lack of information on risk outside CSC, such as time spent in the community on parole.

Enhanced surveillance data indicate that 32% of new admissions were screened for HAV and 39% screened for HBV. Serological immunity among new admissions was 29.9% for HAV and 39.4% for HBV. For general population inmates, 48.2% tested for HAV (serological immunity = 41.2%) and 54.4% tested for HBV (serological immunity = 43.3%). Invoice data on vaccine purchases indicate that enough vaccine was purchased to vaccinate almost two-thirds of new admissions against HAV and/or HBV. From the IDSS, there were no acute HAV cases reported in 2005 and only one case was reported in 2006. From a high of 43 cases diagnosed in 2001, there were 6 acute HBV cases reported in 2005 and 9 in 2006.

The number of syphilis cases in CSC was zero in 2000 and in 2001, compared to 10 in 2004, 6 in 2005 and 16 in 2006, corresponding to a rate of 49 (2005) and 120 (2006) cases per 100,000. Similar increases in overall reported rates were observed for other STIs. The number of chlamydia cases increased from 21 in 2000 to 92 in 2005 (rate of 753 per 100,000) and 95 in 2006 (715 per 100,000). Gonorrhea cases were 11 in 2000 and 2005 (90 per 100,000) and 20 in 2006 (151 per 100,000).

The number of incident active tuberculosis cases reported in CSC varied between 0 - 7 between 1998 and 2006 with 7 cases in 2005 and 3 cases in 2006. This represents active TB rates of 41.1 and 16.3 cases per 100,000, respectively. The rate of latent tuberculosis infection (LTBI) among inmates was 15.8% in 2005 and 16.6% in 2006. Overall, LTBI rates by origin were consistent with reported population-specific rates for sub-populations in Canada (Yuan, 2007). The estimated TST conversion rates among inmates for 2005 – 2006 were 0.90% and 0.89% respectively. This suggests ongoing transmission of TB between inmates (and staff) and the potential for further transmission should converters develop active disease. Continued vigilance to TB screening and surveillance, including tuberculin skin test (TST) screening, source case investigations, contact tracing, and prophylactic treatment of latent TB infection is required.

The validity of the TB surveillance data among staff is influenced by two factors; i) the logistical difficulty in conducting the TB screening tests; and ii) the low TB screening participation rate among staff. The observed LTBI rate, which is slightly higher than the Canadian average, suggest that working in the corrections environment may place staff at higher risk of contracting tuberculosis infection. The estimated TST conversion rates among staff for 2005 – 2006 were 0.82% and 0.66% respectively.

Future Directions

Surveillance data continue to be analyzed. Preliminary data are approved and are used as they are available. Publication of surveillance data makes these data “official”. Following this report, a report for 2007-2008 will be prepared and released. Comprehensive surveillance data with a good baseline and trend measures will assist in evaluating public health program development and harm reduction interventions. CSC is committed to working with other pan-Canadian stakeholders in improving the public health among all Canadians.

 

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