Profile of Hepatitis C & Injection Drug Use in Canada

Epidemiology of HCV

The hepatitis C virus was identified in 1989 (Choo et al., 1989), with a specific test to detect the presence of the virus available in 1990 (Remis, 1998). Serologic tests for HCV are relatively recent, as such there are many areas relating to disease and transmission that are only now being realized (Mather and Crofts, 1999).

Prevalence and Incidence

Although a restricted form of national reporting of HCV infection in Canada started in 1992, it was not until January 01, 1999 that all Canadian provinces and territories were reporting HCV cases (LCDC, 1999). In 1997, a total of 19,571 cases were reported. The prevalence of HCV infection in Canada is estimated at 0.8% (240,000 persons) (Remis, 1998). Worldwide, it is estimated that 3%, or approximately 170 million people are chronic carriers (LCDC, 1999). Most newly or chronically infected persons have no symptoms (approximately 70%), and as such are unaware of their infection (LCDC, 1999; MRC, 1999). They remain a source of transmission and are at risk for chronic liver disease, cirrhosis and liver cancer (LCDC, 1999).

The lack of symptoms, as well as the absence of a test to distinguish new cases from chronic cases, make it very difficult to estimate the incidence of the disease. An enhanced surveillance system to identify cases of acute HCV was established in four Canadian cities in October 1998. The extrapolated results suggest that 911 cases of clinically recognized acute hepatitis C could be identified in Canada. If infections without symptoms (70%) are included in this estimate, the total number of new HCV infections is estimated at 4,500 per year for Canada (Zou, Zhang, Tepper, et al., 2000).

Because of the potentially long lag time between infection and symptoms, a substantial increase in disease sequelae of HCV infection is anticipated in Canada over the next decade (LCDC, 1999). It has been predicted that by the year 2008, the incidence of cirrhosis and end-stage liver disease will have doubled, the incidence of liver cancer will have increased by 70% and liver deaths by 140% (MRC, 1999).

Modes of Transmission

The primary mode of transmission for HCV is through exposure to blood and blood products. The major group infected and at risk of infection is persons who share needles and other drug paraphernalia. In numerous studies of this population, HCV antibody positivity rates have been reported to be higher than 50%, and in some populations, reaching close to 100% (Heintges and Wands, 1997). In Canada, IDU accounts for approximately 70% of all HCV prevalent infections (LCDC, 1999).

Before HCV antibody screening of donated blood became standard practice, 10-15% of individuals who had received multiple blood transfusions or plasma products contracted the virus (LCDC, 1999). The introduction of HCV antibody screening of blood products has led to a dramatic decrease in HCV transmission through this method (Heintges and Wands, 1997). In Canada, the current risk is very low at about 1 in 103,000 units (LCDC, 1999). The Canadian Blood Services and HEMA Québec are currently investigating a new blood screening method (Nucleic Acid Amplification Testing or NAT) that is anticipated to further decrease the risk of transmission to 1 in 500,000 units (Canadian Blood Services, 1999).

Although sexual transmission of HCV infection has been demonstrated, it is not a common mode of transmission. Research in the United States and Europe has found low rates of infection, in the range of 0% to 6%, in partners of individuals with chronic HCV infection. The risk of infection through sexual intercourse with a carrier has been estimated at 2.5% over 20 years (LCDC, 1999). There is evidence to suggest that individuals who engage in frequent multi-partner sexual activity, independent of other factors such as IDU and tattooing, are at increased risk of contracting HCV (Dienstag, 1997).

Scully and colleagues (1993) examined the clinical and epidemiological features of HCV virus infection in a gastroenterology/hepatology practice in Ottawa, Canada. In this study, a retrospective chart review was conducted on 63 consecutive patients identified as anti-HCV positive. The results indicated that 48 (76%) had been exposed to HCV through exposure to blood: 27 used intravenous drugs, and 21 had received blood or blood products. In addition, the long-term sexual partners of 29 of these patients agreed to HCV antibody testing. None of the sexual partners who were tested were anti-HCV positive. The authors concluded that the majority of HCV cases, at least in Ottawa, are acquired through exposure to blood (either through medical treatment or sharing of needles) and that sexual transmission is rare.

Mother to child transmission of HCV is fairly uncommon, occurring in less than 5% of cases. Transmission rates are approximately three times greater if the mother is co-infected with HCV and HIV (Zanetti et al., 1999; Zanetti et al., 1995). There is no definite association between transmission and type of delivery or breast-feeding (Patrick et al., 2000). However, the Canadian Liver Foundation recommends the suspension of breast-feeding if the mother's nipples are bleeding or cracked (Canadian Liver Foundation, 1999).

In other countries, associations have been observed between the use of unsterilized devices in activities that break the skin, such as tattooing, ear or body piercing, or acupuncture, and HCV infection (CDC, 1998). However, research in the US has failed to find a relationship between these practices and HCV infection (CDC, 1998; Silverman et al., 2000). Finally, approximately 10% of people with HCV infection have no known risk factor (LCDC, 1999).

Back