Enhanced surveillance for acute and likely acute hepatitis B in Canada: 1999 to 2002.

OBJECTIVE: To assess the incidence of clinically identified hepatitis B cases, as well as the demographic and risk behaviour profiles of these cases in a defined Canadian population. METHODS: An enhanced hepatitis surveillance system was established in October 1998 to identify acute hepatitis B and C cases in Canada. Acute and likely acute cases, as determined by laboratory testing, collectively defined incident clinical hepatitis B cases. Data from 1999 to 2002 on incidence, demographic characteristics and risk behaviour characteristics were collected and analyzed. RESULTS: During the 1999 to 2002 surveillance period, 379 cases were identified in a target population ranging from 3,128,179 to 8,576,071 individuals. The observed hepatitis B incidence rate was 1.93/100,000 person-years in the surveillance area. The incidence rate was 2.74 times higher in men. The observed incidence rates decreased for all age groups over the surveillance period but remained high in the 20- to 29-year-old and 30- to 39-year-old age groups, as well as in men. Of the incident cases, 55.9% self-identified as being born in Canada and 18.5% as being born in Asia, while 18.7% did not identify a birth area. Of the Canadian-born cases, 61.3% identified themselves as Caucasian, 11.3% as Aboriginal and 23.6% as no ethnic category. Injection drug use was the most reported risk behaviour (19.1%), followed closely by sex-associated risk behaviours. A large proportion, 24%, indicated none of the known risk behaviours. CONCLUSIONS: The hepatitis B incidence rate has shown some decrease in the surveillance population from 1999 to 2002 and this may be due, in part, to past intervention programs (eg, vaccination programs and health promotion campaigns). The authors' results identify some high-risk groups that would benefit from additional prevention and control programs, and further targeted research and intervention.