Epidemiology of hepatitis B in Canada.
OBJECTIVE
To provide a current and comprehensive review of the epidemiology of hepatitis B virus (HBV) in Canada.


METHODS
Published and unpublished epidemiological studies and surveillance reports of the past decade, primarily from Canada were studied. Fifty reports addressing HBV surveillance, incidence and prevalence, transmission-associated risk factors, co-infections, and prevention strategies were reviewed.


RESULTS
HBV infection is an important vaccine-preventable infectious disease in Canada. The incidence rate of clinically recognized, acute HBV infection in 1998/1999 was estimated to be 2.3/100,000 people or approximately 700 cases a year. The prevalence of HBV carriers is estimated to be 0.5% to 1.0% of the population, but varies substantially according to population-specific risk factors. Most acute HBV infections are associated with injection drug use or high risk heterosexual activities, but 20% to 30% of acute cases did not report any identified risk factors. Surveillance activities such as the National Notifiable Disease Reporting system provide information regarding trends and risk factors. The primary preventive strategy for HBV consists of universal immunization for preadolescents and/or infants. Other strategies, such as the universal prenatal screening and postnatal immunization, and the prevention of nosocomial acquisition, are also important. The recently described hepatitis B surface antigen (HBsAg) escape mutants may not be detected by current HBsAg test assays, and the existing HBV vaccines may not protect vaccinees from infections by such mutants.


CONCLUSIONS
Ongoing surveillance and research are required to assess risk factors for HBV transmission, evaluate the effectiveness of immunization programs and monitor the impact of HBsAg escape mutants.
Zhang
J
J
Bloodborne Pathogens Division, Bureau of Infectious Diseases, Centre for Infectious Disease Prevention and Control, Population and Public Health Branch, Health Canada, Ottawa, Ontario. jun_zhang@hc-sc.gc.ca
Zou
S
S
Giulivi
A
A