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Hepatitis A

Hepatitis A is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

One of the world’s most common infections, the hepatitis A virus (HAV) primarily involves the liver.

Epidemiology

Incidence
  • 1.4 million cases globally each year
  • Since routine use of hepatitis A vaccine (1995), the incidence of HAV has decreased by 95%.
  • Approximately 2,000 HAV infections in 2016
  • Incidence in the United States: 0.4/100,000
  • No difference based on sex
  • As many as 1/2 of current HAV infections in the United States are acquired during travel to endemic countries.
  • Incubation period averages 28 days but can be as long as 50 days (range 15 to 50 days).

Prevalence
Serologic evidence of prior HAV infection is present in ~1/3 of U.S. population. Anti-HAV prevalence relates to age, ranging from 9% in children ages 6 to 11 years to 75% of those >70 years; relates inversely to income
Pediatric Considerations
  • Often, milder or asymptomatic in children; severity increases with age.
  • Infections asymptomatic in 70% of children <6 years
  • <50% of 13- to 17-year-olds in the United States are vaccinated.
Pregnancy Considerations
  • Increased risk of complications including preterm labor and premature rupture of membranes
  • 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.
  • Primary transmission is fecal–oral.
  • Humans are the only natural host.
  • Incubation is 2 to 6 weeks (mean 4 weeks).
  • Greatest infectivity is the 2 weeks before and 1 week after onset of clinical illness.
  • Infection occurs primarily after consuming food or water contaminated with HAV or via direct contact.
  • Outbreaks occur through exposure to a common food or water source.
  • Virus is stable in water and on surfaces but is easily killed with high heat or cleaning agents.
  • Shellfish (clams and oysters) may be contaminated if harvested from waters contaminated with HAV.
  • Blood-borne transmission is rare.
  • HAV is not a chronic disease but can last for months.

Genetics
Autoimmune hepatitis is rarely associated with human leukocyte antigen class II; DR3 and DR4 after active infection with HAV

Risk Factors

  • Travel to developing countries accounts for >50% of cases in North America and Europe.
  • Employment in health care
  • Household exposure
  • Intimate exposure, especially men who have sex with other men
  • Injection of illicit drugs
  • Child care centers, schools
  • Institutionalized individuals
  • Clotting factor disorders, such as hemophilia
  • Blood exposure/transfusion (rare)
  • No identifiable risk factor in 50%

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; Twinrix—combination HAV and HBV
  • Vaccine lasts ~25 years or more.
  • Vaccine is recommended for (1)[C],(2)[A]:
    • 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
    • Men who have sex with men
    • Illicit IV drug users
    • Anyone with chronic liver disease (including pre– and post–liver transplant)
    • Individuals with a clotting factor disorder
    • Household members and close contacts of children adopted from countries with a high HAV prevalence (prior to arrival)
    • Anyone exposed during an outbreak
  • Routine vaccination is no longer routinely recommended for food service, child care, or health care workers (1)[C].
  • HIV-infected patients who are negative for HAV IgG should receive HAV vaccine series, preferably early in course of HIV infection.
    • If CD4 count is <200 cells/mm3 or the patient has symptomatic HIV disease, defer vaccination until several months after initiation of antiretroviral (ARV) therapy to maximize antibody response.
    • Hepatitis A vaccine can be given to immunocompromised patients with CD4 count >200.
    • Hepatitis A vaccine is recommended for pregnant women with additional medical conditions (higher risk for HAV infection).
  • HAV is not killed by freezing.
  • HAV is killed by
    • Heating to 185°F for 60 seconds
    • Chlorine
    • Iodine

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Citation

Stephens, Mark B., et al., editors. "Hepatitis A." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2019. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116265/4.0/Hepatitis_A.
Hepatitis A. In: Stephens MB, Golding J, Baldor RA, et al, eds. 5-Minute Clinical Consult. 27th ed. Wolters Kluwer; 2019. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116265/4.0/Hepatitis_A. Accessed July 21, 2019.
Hepatitis A. (2019). In Stephens, M. B., Golding, J., Baldor, R. A., & Domino, F. J. (Eds.), 5-Minute Clinical Consult. Available from https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116265/4.0/Hepatitis_A
Hepatitis A [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2019. [cited 2019 July 21]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116265/4.0/Hepatitis_A.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Hepatitis A ID - 116265 ED - Stephens,Mark B, ED - Golding,Jeremy, ED - Baldor,Robert A, ED - Domino,Frank J, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116265/4.0/Hepatitis_A PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -