Additional information about HB testing is available at the Government of Canada webpage. Chronic carriers express HbsAg, and may have HBeAg and measurable viral DNA in blood. Some individuals with acute HB infection will become chronic carriers. Persons with anti-HBs and anti-HBc are not infectious. This includes those who are currently infected and those who were infected in the past but have cleared the virus. In addition, antibody to HB core antigen (anti-HBc) will appear in persons who have been exposed to the virus. The presence of anti-HBs confers long-term immunity. In severe acute HB infections, anti-HBs may be present simultaneously with HBsAg. In most cases, antibody to HBsAg (anti-HBs) appears after HBsAg has disappeared and the infection has resolved. Persons in the acute stage of HB are considered infectious. HBsAg can be detected in serum 30 to 60 days after exposure and persists until the infection resolves. Two antigens are important in evaluating people with HB infection and are markers of HB carriage: hepatitis B surface antigen (HBsAg), which is present in either acute or chronic infection with HB virus and hepatitis B envelope antigen (HBeAg), which typically is associated with higher viral loads, increased infectivity and more actively replicating virus. The incubation period is 45 to 180 days (average 60 to 90 days). Saliva is considered infectious in bite wounds with broken skin involving the inoculation of saliva, or when it is visibly tainted with blood. The risk of transfusion-related HB is extremely low in Canada and the USA because all blood and blood products are tested. 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 HB cases or carriers to their newborns. HB is transmitted through percutaneous or mucosal contact with infectious biological fluids. For additional information about HB virus, refer to the Government of Canada webpage. Hepatitis B (HB) virus is a deoxyribonucleic acid (DNA) virus of the Hepadnavirdiae family. Epidemiology Disease description Infectious agent Significant revisions included in this chapter are highlighted in the Table of Updates to the Canadian Immunization Guide.
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