A Study to Characterize the Epidemiology of Hepatitis C Infection in Canada, 2002

PDF Version (516 KB, 57 pages)

HP40-31/2008E-PDF 978-0-662-48672-5

Final Report

Hepatitis C Prevention, Support and Research Program Community Acquired Infections Division
Centre for Communicable Diseases and Infection Control
Infectious Disease and Emergency Preparedness Branch Public Health Agency of Canada

Prepared by: Robert S. Remis, MD, MPH, FRCPC

Executive Summary

In 1998, a working group evaluated the extent of hepatitis C infection transmitted through blood transfusion in Canada. In the course of its work, the group estimated that, overall, about 240,000 persons were infected with hepatitis C virus (HCV) in Canada as of July 1998. The working group did not, however, examine the distribution of HCV infection among persons in other exposure categories (such as injection drug use, the most common source of infection), nor did it attempt to estimate the current or future impact of HCV infection. Given the elapsed time since this work was carried out and its limited scope, Health Canada wished to re-examine the estimated prevalence of HCV infection in Canada and to obtain more detailed estimates for each exposure category. This has become particularly pertinent since the Hepatitis C Prevention, Support and Research Program is scheduled to end in March 2004, and the Government of Canada is considering whether to renew this program.

The objectives of this HCV modeling study were to estimate the following parameters: hepatitis C incidence and prevalence (overall and by exposure category); the proportion of HCV infections diagnosed; the number of persons living with HCV infection by stage of disease; HCV-related morbidity; and the future occurrence of serious complications of HCV infection.

The study was carried out in three stages: (1) estimating the populations at risk by place of birth and exposure category; (2) modeling HCV incidence and prevalence among those born in Canada and, for persons born elsewhere, HCV prevalence at the time of arrival and subsequent HCV incidence ; and (3) projecting the outcomes of chronic HCV infection among those infected.

The population was stratified according to birth in Canada versus elsewhere. In each group, we estimated the numbers of persons in four mutually exclusive categories related to the acquisition of HCV infection: injection drug users, hemophilia patients, recipients of blood transfusions, and others. The “Other” category included persons infected by HCV primarily through sexual transmission, exposures of health care workers and non-injecting drug use. The model was run from 1960 to 2022. To estimate the population size in each year accurately, the multiple components of mortality were modeled specifically for each exposure category.

Data from the Enhanced Hepatitis Strain Surveillance System were used to help estimate HCV incidence and to determine the relative proportion of incident and prevalent HCV infections by exposure category and place of birth.

HCV-infected persons may eventually develop serious complications. This was assessed by estimating the number progressing through the following stages: cirrhosis, decompensated cirrhosis (liver failure), hepatocellular carcinoma, liver transplant and liver-related death. The model used annual transition parameters based on published data and modeling studies, incorporating important modifying factors such as age, sex and alcohol intake. The model was treated as an integrated continuum from entry through birth or immigration and then transition to exposure-related behaviours or experiences, mortality, HCV infection and progression to serious HCV disease.

To estimate the impact of HCV infection on increased morbidity, we estimated for each year and cumulatively the deficit in “quality-adjusted life years” (QALYs) in comparison to persons who were not infected with HCV, for each year from 1960 to 2022 and cumulatively since 1960. A questionnaire was sent to provincial representatives to obtain information on the reporting of HCV infection and details of notification programs that encourage transfusion recipients to be tested for HCV infection.

The results of our study may be summarized as follows. We estimated that approximately 251,000 persons in Canada were infected with HCV as of December 2002 and that about 5,000 persons are newly infected each year, mostly through injection drug use. The prevalence of HCV infection in Canada in 2002 was 4% higher than in 1998. The distribution of prevalent HCV infections by exposure category (to the nearest 1,000) was as follows: IDU 50,000, ex-IDU 89,000, hemophilia patients 1,200, blood transfusion recipients 33,000 and “Other” 74,000. In our analysis, IDU accounted for 55.6% of the prevalent HCV infections in Canada, hemophilia for 0.5%, blood transfusions 13.2% and other modes of transmission 29.6%. Overall, about 65% of HCV-infected persons in Canada have received a diagnosis to date.

The impact of the sequelae of hepatitis C infection on the health of Canadians appears to be considerable. In 2002, 9,400 persons were living with cirrhosis and 3,200 with liver failure. The annual incidence of newly developing cirrhosis appeared to peak in the late 1990s and early 2000s but, according to the results of our model, the incidence of the more serious outcomes of HCV infection will continue to rise, at least until 2022. Finally, our results also indicate that the impact of HCV disease on the health of Canadians has been and will continue to be dramatic: to 2002, almost 1,200,000 QALY have been lost from HCV infection and, by 2022, a cumulative total of almost 2,100,000 QALY will have been lost. These results should, nevertheless, be put in the context of other infectious and non-infectious conditions to be fully appreciated.

There are several important lessons to be learned from our study. Clearly, the impact of hepatitis C infection on the health of Canadians is considerable. Measures must be taken to encourage the estimated 90,000 HCV-infected persons whose condition remains undiagnosed to undergo HCV testing. Health care services to treat HCV-infected patients must be made available to all who may benefit from them; these include specialized physician and laboratory services and antiviral drugs. Further research is also required at many levels, including studies to (1) better evaluate the extent and the factors responsible for HCV infection in Canada, (2) develop more effective outreach programs to prevent new infection, (3) improve access to diagnosis and treatment services for underserved populations, (4) better understand HCV infection and disease and (5) develop more effective methods of treatment.

Table of Contents

1. Introduction
2. Study Objectives
3. Methods
   • 3.1 HCV Infection and Outcomes Model – Overview
   • 3.2 Modeling of HCV Prevalence
   • 3.3 HCV Infection Among Persons Not Born in Canada
   • 3.4 Use of Data from the Enhanced Hepatitis Strain Surveillance System (EHSSS)
   • 3.5 HCV Incidence
   • 3.6 Modeling HCV Outcomes
   • 3.7 The Integrated Analytic HCV Model
   • 3.8 Estimating HCV-related Morbidity: Calculation of Quality-adjusted Life Years Lost
   • 3.9 Proportion of HCV Infections Diagnosed and Reported
   • 3.10 Survey of Provincial Health Departments
4. Results
   • 4.1 HCV Prevalence Among Persons Immigrating to Canada
   • 4.2 Analysis of EHSSS Data
   • 4.3 Results of Epidemiologic Modeling: HCV Prevalence
   • 4.4 Results of Epidemiologic Modeling: HCV Incidence
   • 4.5 Results of Epidemiologic Modeling: HCV Outcomes
   • 4.6 Results of Epidemiologic Modeling: HCV Morbidity
   • 4.7 HCV Infections Diagnosed and Reported
   • 4.8 Summary of Generalized Lookback Programs
5. Discussion
6. References