Hepatitis A Virus (HAV) Infection

Background

• Hepatitis A virus (HAV) is one of the most common viral infections worldwide.
• Most of the world's population resides in areas with ongoing moderate risk of transmission of hepatitis A virus.
• The areas of highest endemicity are Africa and South Asia.
• HAV is transmitted by the fecal-oral route.
  • Outbreaks have been associated with consumption of contaminated water or foods, including shellfish, raw vegetables, and recently frozen berries.
  • Other risk factors for HAV infection include close contact with an infected person, daycare, sexual contact (particularly among men who have sex with men), and illicit drug use.
• The incubation period averages about 30 days.
• Acute infection is often asymptomatic. When present, symptoms are often mild and include fever, nausea, vomiting, diarrhea, jaundice, and abdominal pain.
• Extrahepatic manifestations are uncommon, but vasculitis, arthritis, aplastic anemia, hemolytic anemia, thrombocytopenia, pancreatitis, and Guillain-Barre syndrome have been reported.
• In most patients, HAV infection is self-limited, with most patients fully recovering within 2-6 months. This is in contrast to hepatitis B and C viruses which may cause chronic infection.
• Fewer than 1% of patients develop fulminant hepatic failure, which may necessitate liver transplantation and may be fatal.
• Risk factors for fulminant disease include age < 10 years or > 40 years, concurrent liver disease (such as hepatitis C virus infection), and pregnancy.
• Mortality due to HAV in the United States is about 0.3%.

Evaluation

• No clinical feature clearly distinguishes HAV infection from other forms of acute hepatitis.
• Laboratory evaluation may reveal:
  • marked elevation in serum aminotransferases (often > 1,000 units/L) with alanine aminotransferase typically higher than aspartate aminotransferase
  • elevated bilirubin and alkaline phosphatase
• Diagnosis of suspected HAV infection is confirmed by a positive serum HAV immunoglobulin M (IgM).
  • IgM becomes detectable about 5-10 days into symptomatic illness.
  • Sensitivity and specificity is near 100%.

Management

• Treatment is supportive care, focused on bed rest, hydration, and control of nausea and diarrhea.
• No specific antiviral therapy is available for the treatment of hepatitis A virus.
• Evaluation for emergent liver transplantation may be needed for the rare occurrence of fulminant hepatic failure.

Prevention

• HAV vaccination confers a protective antibody response in > 90% of those vaccinated, and immunity is thought to be lifelong.
• Institution of routine vaccination has resulted in marked decreases in incidence of infection in several countries.
• In the United States, vaccination is recommended for all children beginning at age 12 months and for adults with certain risk factors.
• Preexposure prophylaxis should be considered before travel to countries with intermediate to high endemicity of infection for unvaccinated, partially vaccinated, or never infected persons.
  • For persons < 6 months old, give immunoglobulin (Ig).
  • For persons 6-11 months old, give travel-related dose of HAV vaccine (this dose cannot count as part of routine vaccination initiated at age 12 months).
  • For persons 12 months to 40 years old who are healthy, give single dose HAV vaccine as soon as travel considered and complete 2-dose series according to routine schedule.
  • For persons > 40 years old and persons > 6 months old with immunocompromise or chronic liver disease, give single dose HAV vaccine as soon as travel considered and complete 2-dose series according to routine schedule. If traveling in < 2 weeks, consider also administering Ig.
  • For persons who elect not to receive HAV vaccination or in whom HAV vaccine is contraindicated, give Ig.
• Postexposure prophylaxis is recommended as soon as possible for those who have been exposed to HAV within the past 2 weeks and who have not previously received HAV vaccine.
  • Infants < 12 months old should receive Ig.
  • Healthy individuals ≥ 12 months old should receive HAV vaccine.
  • In addition to vaccination, consider Ig for person > 40 years old depending on risk assessment.
  • Individuals ≥ 12 months old with chronic liver disease or immunocompromise should receive both HAV vaccine and Ig (using different anatomic sites).
  • Persons in whom HAV vaccine is contraindicated should receive Ig.