Description

Caused by the hepatitis A virus (HAV) and is a small nonenveloped single stranded RNA virus; HAV infections are common worldwide primarily involving the liver.

Epidemiology

Incidence

• 1.5 million cases globally each year; since the release of the HAV vaccine in 1995, the incidence of HAV 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; however, it remains very high in developing countries 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 with lack of jaundice development 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 linear RNA enterovirus of the Picornaviridae family. Infection is limited to hepatocytes and macrophages. HAV is excreted into the bile and then stool, providing major route of spread. Humans are the only known natural reservoir. Transmission is primarily through fecal-oral route; however, HAV is also transmitted through sexual intercourse (particularly anal-oral contact) and intravenous drug use. Incubation is 2 to 6 weeks with a mean of 4 weeks.
• Disease course is divided in two phases: prodromal phase, which is associated with the development of symptoms (fever, malaise, weakness, anorexia, nausea, vomiting), and convalescent period (jaundice develops).
• Greatest infectivity period is 2 weeks before the appearance of jaundice or elevation of liver enzymes coinciding with peak in viral stool concentration.
• Virus is stable in water and on surfaces but is easily killed with high heat or cleaning agents.
• HAV is not a chronic disease.

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

Risk Factors

• Person-to-person contact:
  • Intimate exposure, particularly anal-oral contact; residential institutional transmission; employment in health care; household exposure; child care centers, schools
• Contaminated food or water contact: Travel to developing countries accounts for >50% of cases in North America and Europe; consumption of raw/undercooked shellfish, vegetables, or other foods; consumption of improperly handled food or contaminated water
• Other modes of transmission: injection of illicit drugs; blood exposure or transfusion (rare); no identifiable risk factor in 50% 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 (1).
• 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 is 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.

Commonly Associated Conditions

HAV can sometimes be associated with rare extrahepatic manifestations.