Hepatitis B Virus - HBV

Hepatitis B Virus - HBV

 

Hepatitis B (HBV) is a blood-borne virus and one of the most common infectious diseases in the world.

Epidemiology

  • Incidence – about 50,000/year
  • Transmission
    • Parenteral
    • Sexual
    • Perinatal vertical
    • Horizontal – from chronically infected person in a household

Organism

  • Eight HBV subgroups (A-H) based on genetic differences
  • Genotype may be associated with disease progression
  • Not directly cytotoxic to hepatocytes
  • Severity of injury is modulated by host immune responses

Risk Factors

  • Intravenous drug abusers
  • Multiple sex partners (more than 1 partner during the preceding 6 months)
  • Men who have sex with men
  • Infants of infected mothers
  • Persons infected with human immunodeficiency virus (HIV)
  • High rates of HBV infection continue to occur among Alaska Native and Pacific Islander children and among children residing in households of first-generation immigrants from countries where HBV infection is endemic

Clinical Presentation

  • Acute HBV
    • Approximately 50% of the people who are infected will have symptoms which usually appear within 25 to 180 days following exposure
    • The mildest attacks are asymptomatic and detectable only by an increase in serum transaminase levels
    • Influenza-like symptoms – fatigue, malaise, fever
    • Jaundice and gastrointestinal symptoms
    • A few develop acute fulminant hepatic failure requiring transplantation

Chronic HBV

  • Phases of infection
    • Immune tolerance
    • Immune clearance
    • Inactive carriers
    • Reactivation
  • Infants and young children are at the greatest risk for becoming chronically infected if exposed to the hepatitis B virus
    • 90% of exposed infants will develop chronic hepatitis
    • 30% of exposed children ages 1-5 will develop chronic hepatitis
    • Only 5% of exposed adults will develop chronic hepatitis
  • Most common findings are fatigue and modestly elevated transaminases
  • Patients may have systemic symptoms that are associated with the deposition of circulating hepatitis B antigen-antibody immune complexes such as arthritis, leukocytoclastic vasculitis, glomerulonephritis, cryoglobulinemia  and generalized vasculitis
  • Long-term consequences include cirrhosis and hepatocellular carcinoma

Diagnosis

  • Laboratory testing
    • Acute – HBV core antibody IgM and HBV surface antigen (HBsAg)
    • Chronic – HBsAg positive for longer than 6 months
      • Monitoring chronic – HBsAg, HBeAg, anti-HBe, anti-HBs, HBV DNA
    • If either the surface antigen or DNA test is positive, the carrier is contagious

Treatment

  • Current therapies are available
    • May be curative or significantly reduce viral load in chronic hepatitis
    • Reduces risk of hepatocellular carcinoma
  • Genotyping prior to therapy may be helpful
    • Certain genotypes are at higher risk for poor response to treatment

Prevention

  • Vaccination is recommended for:
    • Persons who reside in a community with an increased prevalence of infection
    • Persons who will travel to a country with high prevalence rates
    • Health care workers
    • All neonates and children
    • HIV positive patients
    • Prisoners

See Also