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One of the world’s most common infections, the hepatitis A virus (HAV) primarily involves the liver.
- 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).
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
- 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.
- 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.
Autoimmune hepatitis is rarely associated with human leukocyte antigen class II; DR3 and DR4 after active infection with HAV
- 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%
- 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