If they feel your condition would endanger the health or safety of the Canadian population or cause excessive demand on existing social or health services they will reject the application. Hepatitis B is a contagious liver infection and if CIC receive a positive Hepatitis B result then your chances would be slim, and you may get a rejection.
Piece of advice, you shouldn't even be worrying about a visa if there is a chance you may have Hepatitis B. I suggest you get tested again and go to a different panel physician to make sure it wasn't a false positive. Don't put your visa before your health!