Hepatitis A

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Basics

Description

Hepatitis A infections are caused by the hepatitis A virus (HAV), a member of the Hepatovirus genus. This virus is one of the world’s most common infections and primarily involves the liver. HAV is one of several types of hepatitis viruses that can lead to liver injury. However, compared to the other hepatitis viruses, HAV has distinct features that set it apart.

Epidemiology

Incidence
  • 1.4 million cases globally each year
  • Since routine use of the hepatitis A vaccine (1995), the incidence of HAV has decreased by 95%.
  • Approximately 4,000 HAV infections occurred in 2016.
  • Between 2016 and 2018, reports of hepatitis A infections increased by 294% from 2013 to 2015.
  • No difference in infection rates 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 about 28 days (range 15–50 days)

Prevalence
Serologic evidence of prior HAV infection is present in approximately 1/3 of the 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.

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.
  • Primary transmission is fecal–oral.
  • Can also transmit through sexual intercourse (particularly anal–oral contact) and intravenous drug use.
  • 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.
  • 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.
  • HAV is not a chronic disease but can last for several months.

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

Risk Factors

  • Person-to-person contact:
    • Intimate exposure, particularly among men who have sex with men
    • Residential institutional transmission
    • Transmission among military personnel
    • Employment in health care
  • 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
  • Other modes of transmission:
    • Injection of illicit drugs
    • Blood exposure or 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 through HAV vaccines:
    • Havrix and Vaqta—inactivated vaccine
    • Twinrix—combination HAV and HBV
  • Vaccine thought to provide protection for 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 (parts of Africa and Asia)
    • Men who have sex with men
    • Illicit IV drug users
    • Those with chronic liver disease (including pre– and post–liver transplant patients)
    • 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 the HAV vaccine series, preferably early in course of HIV infection (1)[C].
    • 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 cells/mm3.
    • 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

Commonly Associated Conditions

HAV can sometimes be associated with more rare extrahepatic manifestations such as:

  • Glomerulonephritis
  • Cryoglobulinemia
  • Optic neuritis
  • Myocarditis
  • Thrombocytopenia, aplastic anemia, or red cell aplasia
  • Leukocytoclastic vasculitis

-- To view the remaining sections of this topic, please or --

Basics

Description

Hepatitis A infections are caused by the hepatitis A virus (HAV), a member of the Hepatovirus genus. This virus is one of the world’s most common infections and primarily involves the liver. HAV is one of several types of hepatitis viruses that can lead to liver injury. However, compared to the other hepatitis viruses, HAV has distinct features that set it apart.

Epidemiology

Incidence
  • 1.4 million cases globally each year
  • Since routine use of the hepatitis A vaccine (1995), the incidence of HAV has decreased by 95%.
  • Approximately 4,000 HAV infections occurred in 2016.
  • Between 2016 and 2018, reports of hepatitis A infections increased by 294% from 2013 to 2015.
  • No difference in infection rates 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 about 28 days (range 15–50 days)

Prevalence
Serologic evidence of prior HAV infection is present in approximately 1/3 of the 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.

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.
  • Primary transmission is fecal–oral.
  • Can also transmit through sexual intercourse (particularly anal–oral contact) and intravenous drug use.
  • 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.
  • 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.
  • HAV is not a chronic disease but can last for several months.

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

Risk Factors

  • Person-to-person contact:
    • Intimate exposure, particularly among men who have sex with men
    • Residential institutional transmission
    • Transmission among military personnel
    • Employment in health care
  • 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
  • Other modes of transmission:
    • Injection of illicit drugs
    • Blood exposure or 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 through HAV vaccines:
    • Havrix and Vaqta—inactivated vaccine
    • Twinrix—combination HAV and HBV
  • Vaccine thought to provide protection for 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 (parts of Africa and Asia)
    • Men who have sex with men
    • Illicit IV drug users
    • Those with chronic liver disease (including pre– and post–liver transplant patients)
    • 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 the HAV vaccine series, preferably early in course of HIV infection (1)[C].
    • 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 cells/mm3.
    • 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

Commonly Associated Conditions

HAV can sometimes be associated with more rare extrahepatic manifestations such as:

  • Glomerulonephritis
  • Cryoglobulinemia
  • Optic neuritis
  • Myocarditis
  • Thrombocytopenia, aplastic anemia, or red cell aplasia
  • Leukocytoclastic vasculitis

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