HB is transmitted through percutaneous or mucosal contact with infectious biological fluids. Transmission of HB occurs through close contact with infectious bodily fluids, including through sharing of injection drug equipment (such as needles), sexual contact, and from mothers who are acute cases or carriers to their newborns. The risk of transfusion-related HB is extremely low because all blood and blood products are tested. Saliva is considered infectious in bite wounds with broken skin involving the inoculation of saliva, or when it is visibly tainted with blood. Almost one-third of people with HB infection have no identified risk factors.
The highest risk of transmission and of subsequent chronic carriage is in infants exposed during child birth to their mothers who are carriers of HB. Other groups at higher risk of HB include injection drug users, households with HB carriers and people at risk of sexually transmitted diseases. In Canada, most cases of acute HB occur in unimmunized people 25 years of age and older who acquire infection through unprotected sexual activity, sharing injection drug equipment, household contact with an HB carrier, or treatments or procedures with percutaneous exposure. People on dialysis are considered at high risk. A high proportion of HB carriers in Canada are immigrants from HB endemic areas.
Source : Public Health Agency of Canada