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Canada Communicable Disease Report

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Volume: 27S3 • September 2001

Viral Hepatitis and Emerging Bloodborne Pathogens in Canada

Hepatitis B in Canada

Jun Zhang, Shimian Zou, Antonio Giulivi


The magnitude of hepatitis B infection

Hepatitis B is an important vaccine-preventable infectious disease in Canada. The incidence rate of clinically recognized acute hepatitis B has been estimated to be 2.3 per 100,000, indicating approximately 700 cases a year. The rate is higher among males (3.0 per 100,000) than females (1.5 per 100,000) and peaks for those aged 30-39 (6.1 per 100,000) followed by those aged 15-29 (2.7 per 100,000) and 40-59 (1.8 per 100,000)(1). Acute hepatitis B virus (HBV) infection is asymptomatic in 90% of infants and young children and in 50% to 70% of adolescents and adults(2). Infection in infancy and early childhood is strongly associated with progression to chronic HBV infection, contributing to a significant proportion of chronic liver diseases. The prevalence of hepatitis B has been estimated to be between 0.5% and 1.0% with substantial variation due to the heterogeneity of the population(3). The prevalence of hepatitis B surface antigen (HBsAg) has been reported to be high in immigrant populations (7.4%) and the Inuit (6.9%)(4,5); intermediate among First Nations (0.3%), adolescents (0.4%), STD clinic visitors (0.3%), and residents of long-term care facilities (0.6%)(6-9); and low in the general population(10).

Transmission patterns and risk factors

HBV is transmissible through several routes: 1) percutaneous - injection drug use, exposure to contaminated blood or body fluid; 2) sexual - heterosexual or male homosexual activities; 3) vertical - from mother to infant; and 4) horizontal - between children and household contacts through skin lesions or sharing of blood-contaminated toothbrushes and razors(11).

In Canada, the major risk factors associated with acute hepatitis B infection include injection drug use (IDU) (34%) and heterosexual activities such as having multiple heterosexual partners (24%) and sex with HBV-infected individuals (12%). Drug snorting (2.4%), receipt of blood products (2.4%), male homosexual activity (7.3%), a hepatitis B carrier in the family (2.4%), association with an institution (2.4%), history of hospitalization (7.3%), and surgery (2.4%) or dental visit (2.4%) also account for a proportion of acute cases. In about 27% of acute hepatitis B cases there is failure to identify any risk factor(1). For remote hepatitis B cases, a high proportion report a history of blood transfusion (10.0%), body piercing (13.8%), and occupational blood contact (5.0%). In comparison with acute cases, a much smaller proportion (11.2%) report IDU as a risk factor.

A recent study conducted by Roy et al(12) showed that injection drug use increased the risk of acquiring hepatitis B by a factor of 4.5 (95% confidence intervals [CI] 1.5-8.3). Although reported as risk factors, tattooing and body piercing did not show a statistically significant association with risk (for tattooing, odds ratios [OR] = 1.6, 95% CI 0.6-4.2; for body piercing, OR = 1.6, 95% CI 0.8-3.6).

Co-infection with other bloodborne pathogens

Co-infection of HBV with other bloodborne pathogens, such as hepatitis C virus (HCV), hepatitis delta virus (HDV), and human immunodeficiency virus (HIV), may affect the natural history or clinical severity of HBV infection(13). HBV-HCV coinfection seems to increase the severity of chronic hepatitis B, especially the risk of development of hepatocellular carcinoma. HDV infection among hepatitis B patients increases not only the risk of fulminant liver disease but also the risk and severity of chronic hepatitis B. On the other hand, IDUs infected with HIV and HBV are more likely to be asymptomatic but also more likely to become chronic hepatitis B carriers. Hepatitis B carriers infected with HAV are more likely to have fulminant hepatitis.

Public health surveillance

Hepatitis B has been reportable through the National Notifiable Disease Reporting system since 1969(14). Physicians and laboratories are required to report clinically diagnosed or laboratory-confirmed hepatitis B cases to their local health authority. Cases that meet the hepatitis B surveillance case definition(15) are officially reported to provincial/territorial public health authorities. However, the inconsistent reporting practices across jurisdictions and the lack of information on risk factors have limited the usefulness of the data.

To address the surveillance needs and the information gaps, an enhanced surveillance system for hepatitis B and C has been established in six health units (region or province) and covers about 15% of the Canadian population(1). The objective is to identify acute hepatitis B and C cases in order to estimate the incidence, monitor incidence trends, and examine risk factors associated with transmission of these acute cases. A consensus protocol and standardized case definitions and questionnaire were developed and are used by all six health regions. Each of the health regions assigns one or more public health nurses as investigator(s). Information on demographic factors, clinical characteristics, and laboratory test results are collected through contact with physicians and laboratories while information on potential risk factors are obtained from a telephone interview with hepatitis B patients. Data from each health unit are sent to HC on a monthly basis to update the estimates of incidence and to evaluate the risk factors.

Prevention and control

To prevent hepatitis B in Canada, a comprehensive strategy has been developed and carried out through various federal/provincial/territorial programs(16-18). To prevent vertical transmission, all pregnant women are required to undergo testing for HBsAg during prenatal visits or at the time of delivery. Infants born to HBV-infected mothers should receive hepatitis B immune globulin (HBIg) within 48 hours after birth and a course of three doses of hepatitis B vaccine within 6 months after birth(16), measures that reduce the risk of vertical transmission by more than 90%(19).

HC has developed guidelines for prevention and control of nosocomial hepatitis B(17). These include, for example, the prevention of HBV transmission from patients to health care workers through education and vaccination; the prevention of HBV transmission from patient to patient through blood donor screening and the use of single-use needles and syringes; and the prevention of HBV transmission from health care workers to patients through medical evaluation, risk assessment, and counselling.

Hepatitis B vaccination has been recommended for all individuals at increased risk, such as homosexual/bisexual men, persons with a recent history of STDs or multiple sexual partners, injection drug users, inmates of correctional facilities, household and sexual contacts of HBV-infected persons, and health care and emergency service workers(18). A school-based universal hepatitis B vaccination program targeting pre-adolescents aged 9 to 13 has been implemented in all provinces and territories since the early 1990s(16). The vaccination completion rates are high (91% to 93%)(20), and it is anticipated that the program may prevent 63% of all acute hepatitis B infections and 47% of chronic infections(21). However, the current program, without complementary infant vaccination, will not prevent the proportion of chronic hepatitis B cases (10% to 15%) that occur as a result of infection in infancy or early childhood(22). A recent study has suggested that a universal infant hepatitis B vaccination program may be more efficient and cost-effective in stable and low incidence regions than the universal pre-adolescent programs(23). Currently, a few provinces/territories (including New Brunswick, Northwest Territories, Prince Edward Island and the Yukon Territory) have undertaken a universal infant plus pre-adolescent vaccination program(16).

Although hepatitis B vaccination is safe and effective, the duration of the protection induced by the vaccination is not clear. Increasing evidence, however, suggests long-term protection(24). More specifically, the antibody response rate has been shown to be high in the general population (90% to 95%) and, as might be expected, is lower in immuno-compromised individuals such as those infected with HIV (50% to 70%), patients with diabetes mellitus (70% to 80%), and seniors aged 60 and older (50% to 70%)(18). It has been suggested that hepatitis B vaccine may induce hepatitis B surface antigen mutants or variants(25). Such variants may not be detected by current test assays, and anti-HBs antibodies induced by HBV vaccine may not protect the host against the infection. It is suggested that such variants may not be detected by current screening methods or may infect individuals who have developed protective levels of anti-HBs after the vaccine(26).

Public health responses following identification of infected individuals may also play an important role in prevention and control. These include tracing and notification of sexual/household contacts and providing passive (HBIg) and active (vaccination) immunization. In addition, strategies that are aimed at public health education and promotion of behaviour change, such as reducing the number of sexual partners and discouraging initial drug use, are warranted.

References

  1. Zou S, Zhang J, Tepper M et al. Enhanced surveillance of acute hepatitis B and acute hepatitis C in four health regions in Canada 1998-1999. Can J Infect Dis (in press).

  2. Shapiro CN. Epidemiology of hepatitis B. Pediatr Infect Dis J 1993;12:433-37.

  3. Sherman M. The epidemiology of hepatitis B in Canada. The Hepatitis Information Network Hepatitis Update. June 1996. http://www.hepnet.com/update5.html

  4. Delage G, Montplaisir S, Remy-Prince S et al. Prevalence of hepatitis B virus infection in pregnant women in the Montreal area. Can Med Assoc J 1986;134:897-901.

  5. Baikie M, Ratnam S, Bryant DG et al. Epidemiologic features of hepatitis B virus infection in Northern Labrador. Can Med Assoc J 1989;141:791-95.

  6. Martin JD, Mathias RG. HIV and hepatitis B surveillance in first nations alcohol and drug treatment centers in British Columbia, Canada. Int J
    Circumpolar Health 1998;57(Suppl 1):280-84.

  7. Dobson S, Scheifele D, Bell A. Assessment of a universal school-based
    hepatitis B vaccination program.     JAMA 1995:274:1209-13.

  8. Romanowski B, Campbell P. Sero-epidemiologic study to determine the prevalence and risk of hepatitis B in a Canadian heterosexual sexually
    transmitted disease population.     Can J Public Health 1994;85:205-07.

  9. Simor AW, Gordon M, Bishai FR. Prevalence of hepatitis B surface
    antigen, hepatitis C antibody, and HIV-1 antibody among residents of a long-term-care facility.     J Am Geriatr Soc 1992;40:218-20.

  10. Glasgow KW, Schabas R, Williams DC et al. A population-based
    hepatitis B seroprevalence and risk factor study in a Northern Ontario town.     Can J Public Health 1997;88:87-90.

  11. Tepper M, Gully P. Hepatitis B. Can Med Assoc J 1997;156:1033-34.

  12. Roy E. Haley N, Lemire N et al. Hepatitis B virus infection among street youths in Montreal. Can Med Assoc J 1999;161:689-93.

  13. Levine OS, Vlahov D, Nelson KE. Epidemiology of hepatitis B virus infections among injecting drug users: seroprevalence, risk factors, and viral interactions. Epidemiol Rev 1994;16:418-35.

  14. Sockett PN, Garnett MJ, Scott C. Communicable disease surveillance: notification of infectious disease in Canada. Can J Infect Dis 1996;7:293-95.

  15. Advisory Committee on Epidemiology and Bureau of Communicable Disease Epidemiology. Canadian Communicable Disease Surveillance
    System: disease specific case definitions and surveillance methods    . CDWR 1991;17S3:16-7.

  16. National Advisory Committee on Immunization. Canadian national immunization report: program update. Paediatr Child Health 1999;4(Suppl C):30c-33c.

  17. LCDC. Infection Control Guidelines: preventing the transmission of bloodborne pathogens in health care and public services settings. CCDR 1997;23S3:1-43.

  18. National Advisory Committee on Immunization. Hepatitis B vaccine. In: Canadian immunization guide, 5th edition. Ottawa: Health Canada, 1998:90-102 (Minister of Public Works and Government Services Canada, Cat. No. H49-8/1998E.)

  19. Eleftheriou A, Kalakoutis G, Pavlides N. Transfusion transmitted viruses in pregnancy. J Pediatr Endocrinol Metabolism 1998;11:901-14.

  20. Munroe V, Pielak K. A school-based hepatitis B immunization program for British Columbia. Can J School Health 1996;66:229-32.

  21. Krahn M, Guasparini R, Sherman M et al. Costs and cost-effectiveness of a universal, school-based hepatitis B vaccination program. Am J Public Health 1998;88:1638-44.

  22. Tepper ML. Universal hepatitis B immunization: young adolescent immunization. Vaccine 1998;16:S23-S26.

  23. Wiebe T, Fergusson P, Horne D et al. Hepatitis B immunization in a low-incidence province of Canada: comparing alternative strategies. Med Decis Making 1997;17:472-82.

  24. West DJ, Calandra GB. Vaccine induced immunologic memory for hepatitis B surface antigen: implications for policy on booster vaccination. Vaccine 1996;14:1019-27.

  25. Carman WF, Zanetti AR, Kareylannis P et al. Vaccine-induced escape mutant of hepatitis B virus. Lancet 1990;336:325-29.

  26. Zuckerman AJ, Zuckerman JN. Molecular epidemiology of hepatitis B virus mutants. J Med Virology 1999;58:193-95.

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