HEPATITIS A VIRUS


I. Pathophysiology & Epidemiology

  1. An RNA virus (enterovirus)
  2. Most common in South East Asia & Middle East
  3. High viral titers found in stool & serum (hence fecal-oral xmission) of infected people; low in saliva, semen, urine
  4. Stool virus concentrations peak about 2 weeks before onset of symptoms, and are usually negligible within 1 week after onset of jaundice (may be longer in children).

II. Clinical features:

  1. Often asymptomatic in children < 3yo
  2. Acute, self-limited hepatitis; 99% without complications
  3. Rarely, get fulminant, cholestatic, or relapsing hep.
  4. Other clinical features
    1. Malaise
    2. Fever
    3. Jaundice (more common in adults)
    4. Abdominal pain
  5. Symptoms and transaminase elevations usually resolve within two months of onset
  6. No association with liver cancer 
  7. IgM peaks @ 8wks, followed later by protective IgG

III. Treatment

  1. Post-exposure (<2wk) Ig prophylaxis--us aren't immune if don't get sick
  2. Supportive tx if get clinical hepatitis

IV. Prevention

  1. Gamma-globulin
    1. Effective for post-exposure prophylaxis if given within 2 weeks of exposure
    2. Can be used for pre-exposure prophylaxis as well.  Protection lasts for up to 3mos
    3. Used as an alternative to vaccine for children < 2yo if needed e.g. for travel to high-prevalence regions
    4. Standard dose = 0.02 mL/kg; higher doses (up to 0.06 mL/kg) may offer longer-lasting protection
    5. Gamma-globulin may interfere with live vaccines but there is not thought to be a clinically significant interference with the Hepatitis A vaccine.
  2. Hepatitis A vaccine
    1. As of 2006 recommended by US ACIP for all children at 1yo
    2. Two versions marketed in U.S. ("Havrix" and "Vaqta"); both inactivated, both similarly efficacious
    3. 0.5mL for ages 2-18, 1.0mL for > 18yo
    4. 2 doses 6-12mos apart
  3. In a study in close contacts of pts with Hepatitis A, aged 2y-40yo, all < 14d post-exposure, randomized to Hep A immune globulin x 1 vs. Hep A vaccine x 1; there was no sig. diff. between the groups in the incidence of symptomatic hepatitis A. (NEJM 357:1685, 2007--JW)