Hepatitis A

Descriptive text is not available for this image BASICS

DESCRIPTION

Hepatotropic infection caused by the hepatitis A virus (HAV), a small RNA virus.

EPIDEMIOLOGY

Incidence

  • The most common acute viral hepatitis worldwide with 150 million cases globally each year (1).
  • Since the release of the HAV vaccine in 1995, incidence in the United States has decreased significantly. Regional outbreaks contribute to ongoing disease.
  • As many as 1/2 of current HAV infections in the United States are acquired during travel to endemic countries.

Prevalence

  • Serologic evidence of prior HAV infection is present in approximately 1/3 of the U.S. population.
  • Seroprevalence for HAV has been decreasing in many parts of the world but remains high in developing nations where HAV tends to occur within the first few years of life.

Pediatric Considerations
Often, milder or asymptomatic in children; severity increases with age. Asymptomatic infections occur in 70% of children aged <6 years.Pregnancy Considerations
Increased risk of complications; vertical transmission has been reported; fecal-oral transmission during birth is possible. Breastfeeding is not contraindicated.

ETIOLOGY AND PATHOPHYSIOLOGY

  • HAV is a single-stranded, positive-sense linear RNA enterovirus of the Picornaviridae family. Infection is primarily within hepatocytes. HAV is excreted into the bile and then stool, providing major route of spread. Humans are the only known natural reservoir. Transmitted primarily through fecal-oral route (contaminated food); transmission is also possible sexually and parenterally. Incubation is 2 to 6 weeks with a mean of 4 weeks.
  • Disease course is divided into four phases: Incubation phase (asymptomatic); prodromal phase (fever, malaise, anorexia, nausea, vomiting); icteric phase (presence of dark-colored urine, pale-colored stools, jaundice, and right upper quadrant pain); convalescent phase (resolution of symptoms). It does not cause chronic disease.
  • Greatest infectivity period is 2 weeks before the appearance of jaundice or elevation of liver enzymes when HAV concentration is highest in the stool.
  • Virus is stable in water and on surfaces but is easily killed with high heat or cleaning agents.

Genetics

Autoimmune hepatitis is rarely associated with HLA class II DR3, DR13, and DR4 after infection with HAV.

RISK FACTORS

  • Person-to-person contact:
    • Intimate exposure, particularly anal-oral contact; residential institutions; employment in health care; household exposure; child care centers, schools
  • Consumption of improperly handled food or water: Travel to developing countries accounts for >50% of cases in North America and Europe; consumption of raw/undercooked shellfish, vegetables, or other foods.
  • Other modes of transmission: injection of illicit drugs; blood exposure or transfusion (rare); no identifiable risk factor in 60% of cases

GENERAL PREVENTION

  • Proper sanitation and personal hygiene (hand washing), especially for food handlers, health care, and daycare workers
  • Active immunization HAV vaccines: Havrix and Vaqta or Twinrix—combination HAV and HBV; vaccine provides protection for >20 years (2).
  • Vaccine is recommended for:
    • All children aged 12 to 23 months, with catch-up administration until 18 years old; all travelers to countries with high endemic rate of hepatitis A (parts of Africa, Central and South America, and South and Southeast Asia)
    • Men who have sex with men; individuals using (primarily illicit) injection and noninjection drugs; individuals with occupational risks; pregnant women, if risk of infection or severe outcomes is present; all individuals ≥1 year of age with HIV
    • Chronic liver disease (including pre– and post–liver transplant patients); household members and close contacts of children adopted from countries with a high HAV prevalence (prior to arrival); individuals experiencing homelessness or unstable housing; unvaccinated individuals exposed during an outbreak
  • Routine vaccination no longer recommended for those receiving blood products to treat clotting disorders.
  • HAV is not killed by freezing; HAV is killed by heating surfaces, supplies, or food to >185°F for 60 seconds; direct contact with chlorine is also virucidal.
  • Eligible patients should receive post-exposure prophylaxis within 14 days of exposure.

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