Hepatitis A is a viral disease caused by the hepatotropic hepatitis A virus (HAV) and usually spreads through fecal-oral transmission. About half of all patients with hepatitis A in the US acquire the HAV during visits to countries in which HAV is endemic (tropical or subtropical regions). HAV infection can cause acute viral hepatitis, which initially manifests with prodromal symptoms (fever and malaise), followed by jaundice. The laboratory findings in hepatitis A are similar to those observed in other forms of acute viral hepatitis and include high serum transaminase levels and mixed hyperbilirubinemia. Serological detection of anti-HAV IgM antibodies confirms the diagnosis of hepatitis A. While prodromal symptoms typically resolve within a few weeks, jaundice may persist for 1–3 months. Hepatitis A is typically self-limited with no chronic sequelae, and acute liver failure rarely occurs; therefore, only supportive care is typically required. In the US, routine immunization against HAV is recommended for all children > 12 months of age. Individuals at increased risk of infection, such as travelers to areas in which HAV is endemic, as well as individuals at increased risk of severe disease, such as those with chronic liver disease, should also be immunized against HAV if they have not been previously vaccinated. The hepatitis A immunization series generally provides long-term immunity, without the need for booster doses.
Hepatitis E, caused by the hepatitis E virus (HEV), which is also spread through fecal-oral transmission, is an important differential diagnosis. The clinical features of hepatitis E are almost identical to those of hepatitis A, with the exception that pregnant women are at a higher risk of developing acute liver failure with hepatitis E. Serological tests help to distinguish hepatitis E from hepatitis A.
- Incidence (in the US): ∼ 2,000 cases per year (50% acquired during travels abroad) 
- Age: Vaccination programs have made the disease fairly rare in children; infection is now more widespread in adults. 
Epidemiological data refers to the US, unless otherwise specified.
Pathogen: hepatitis A virus 
- Belongs to the family of Picornaviridae and the genus Hepatovirus
- Small (27 nm in diameter), non-enveloped virus with single-stranded, positive-sense RNA
- Resistant to denaturation by gastric acid, heat, and chemicals, and can remain viable for months in fresh and saltwater
- Humans are the only reservoir for the hepatitis A virus. 
Route of transmission: fecal-oral ; 
- Contaminated water and food (e.g., raw shellfish)
- Risk groups: nursing home residents, international travelers, prison inmates, men who have sex with men, IV drug users.
- Infectious period: 2 weeks before to 1 week after the onset of the illness 
When it comes to viral hepatitis, vowels (A and E) are bowels (transmitted feco-orally).
- Incubation period: 2–6 weeks
- Phases of acute viral hepatitis 
- Potential complications: cholestasis, relapsing HAV infection, and autoimmune hepatitis
- Prognosis 
Laboratory testing 
- Routine studies
↑ Anti-HAV IgM antibodies: present in patients with active infection
- Usually detectable 5–10 days after exposure and 5–10 days before clinical symptoms develop
- Levels peak commonly ∼ 1 month after infection.
- May persist for up to 6 months after infection
↑ Anti-HAV IgG antibodies
- Develop during active infection and persist indefinitely after infection or vaccination
- Production begins within 2–3 weeks of infection.
- HAV RNA can be detected in stool and serum samples using PCR.
- ↑ Anti-HAV IgM antibodies: present in patients with active infection
The presence of anti-HAV IgM antibodies or HAV RNA confirms active hepatitis A. Detection of anti-HAV IgG antibodies in the absence of anti-HAV IgM antibodies indicates immunity against HAV due to prior infection or vaccination. 
Further diagnostic testing is not routinely necessary but may be used to rule out differential diagnoses or in fulminant hepatitis. If performed, additional tests may show the following findings if acute viral hepatitis is present:
- Liver biopsy: not routinely indicated 
- Ultrasound 
For an overview comparing the different types of viral hepatitis see “.”
Hepatitis E 
Pathogen: hepatitis E virus (HEV)
- The hepatitis E virus, which belongs to the family of Hepeviridae and the genus Orthohepeviridae; , is a small (34 nm in diameter), non-enveloped virus with single-stranded, positive-sense RNA.
- HEV genotypes 1 and 2 are found only in humans, but genotypes 3 and 4 are zoonotic diseases with reservoirs in both humans and animals (e.g., pigs, monkeys, and dogs). 
- Route of transmission: : fecal-oral (especially via contaminated water, food, or sources)
- Pathophysiology: The degree of hepatic injury is usually mild and the patient may present with clinical features of acute hepatitis.
Clinical features: similar to those of hepatitis A (see “Clinical features” above). 
- Incubation period: 2–8 weeks
- In the majority of cases, the disease is self-limiting with complete recovery.
- Fulminant hepatitis in pregnant women (high risk of mortality for both mother and fetus)
- Affected individuals do not become carriers nor do they develop chronic hepatitis (unlike in hepatitis B and hepatitis C). 
- Laboratory findings are the same as in hepatitis A.
- Confirmatory test
- Liver biopsy (not normally necessary): patchy necrosis
- Treatment: supportive care
- Prevention: no vaccine available
A fulminant course is relatively common in pregnant women with HEV infection (occurring in up to 20% of cases) and is life-threatening for both the mother and fetus.
The differential diagnoses listed here are not exhaustive.
- Hepatitis A is generally self-limited.
- Offer supportive care. 
- Recommend alcohol avoidance.
- Use medications that are metabolized by the liver with caution (e.g., acetaminophen).
- More intensive treatment may be required in rare cases in which hepatitis A leads to acute liver failure.
Hepatitis A preexposure prophylaxis 
- Advise all travelers to follow primary preventive measures such as .
Hepatitis A vaccine
Recommend routine active immunization for:
- All children > 12 months of age (see “”)
- Individuals at increased risk of infection, including those who:
- Individuals at increased risk of severe disease
- Any individual requesting to be vaccinated
- Consider active immunization for:
- Individuals in settings with people at increased risk of infection (e.g., homeless shelters, needle exchange programs, group homes)
- Individuals at increased risk of HAV infection, including currently or recently incarcerated individuals, during outbreaks
- Two single-antigen inactivated hepatitis A vaccines and one combination hepatitis A and hepatitis B inactivated vaccine are available in the US.
Hepatitis A postexposure prophylaxis 
Postexposure prophylaxis is indicated for all previously unvaccinated individuals who have been in contact with an individual with serologically confirmed hepatitis A within the past two weeks. Hepatitis A is a notifiable disease.
|Recommended regimens for hepatitis A postexposure prophylaxis|
|Type of postexposure prophylaxis||Indications|
|Active immunization|| |
|Passive immunization with immune globulin|
|Both active and passive immunization|