The HBV is a double-stranded DNA hepadnavirus.6 There are at least eight genetic genotypes (A-H) and numerous subgenotypes. The predominant genotypes observed in the United States are A, D, and G. The virus is transmitted through contact with infected blood and other potentially infectious material (OPIM), e.g., saliva, semen, and vaginal secretions. Healthcare and public safety personnel are at risk for occupational exposure.
The HBV may cause either acute and/or chronic inflammatory liver disease. After an incubation period of about 90 days, acute infection is characterized by a prodromal phase of anorexia, nausea, vomiting, malaise, and fever. Urticaria and arthralgia may occur. After 3 to 10 days the urine darkens. Jaundice, if present, peaks in 1-2 weeks and fades during a 2 to 4-week recovery phase. About 90% of the patients experience complete recovery, with persistent immunity.
About 10% of the patients develop chronic HB infection. Some may remain asymptomatic for years, decades, or even for life. Others may experience alternating periods of asymptomatic calm interrupted by periods of malaise, anorexia, fatigue, low-grade fever, and upper abdominal discomfort. Jaundice is variable and is often absent. Still others experience a relentless progression of chronic hepatitis to cirrhosis of the liver, and, finally, to hepatocellular carcinoma.
Infection with the HBV is vaccine-preventable. The hepatitis B recombinant vaccine (Engerix-B, Recombivax-HB) confers long-term protection against clinical illness and chronic HBV infection among persons with normal immune status and boosters are not recommended. Booster doses of the vaccine are recommended for immunocompromised patients and those on hemodialysis when anti-HBs levels decline to <10mIU/mL.
There are no medications available to treat acute HBV infection. Following exposure to blood and OPIM known to be HBsAg-positive, unvaccinated or incompletely vaccinated persons should undergo passive immunization with hepatitis B immune globulin (HBIG) as soon as possible after exposure (preferably within 24 hours). The effectiveness of HBIG when administered more than 7 days after an exposure is unknown.
Currently, there are 5 oral antiviral agents (adefovir, entecavir, lamivudine, tenofovir, and telbivudine) and 2 interferons (interferon alfa-2b and peginterferon alfa-2a) available for the treatment of chronic HBV infections. The optimal duration of treatment is unknown, but many patients are treated for up to 5 years and some may be treated indefinitely. Persons with chronic HBV infection require regular medical monitoring.