Hepatitis A, caused by infection with the hepatitis A virus (HAV),
has an incubation period of approximately 28 days (range: 15� days).
HAV replicates in the liver and is shed in high concentrations in feces
from 2 weeks before to 1 week after the onset of clinical illness. HAV
infection produces a self-limited disease that does not result in chronic
infection or chronic liver disease.
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Hepatitis A, caused by infection with the hepatitis A virus (HAV),
has an incubation period of approximately 28 days (range: 15� days).
HAV replicates in the liver and is shed in high concentrations in feces
from 2 weeks before to 1 week after the onset of clinical illness. HAV
infection produces a self-limited disease that does not result in chronic
infection or chronic liver disease.
However, 10%�% of patients might experience a relapse of symptoms
during the 6 months after acute illness. Acute liver failure from hepatitis
A is rare (overall case-fatality rate: 0.5%). The risk for symptomatic
infection is directly related to age, with >80% of adults having symptoms
compatible with acute viral hepatitis and the majority of children having
either asymptomatic or unrecognized infection. Antibody produced in
response to HAV infection persists for life and confers protection against
reinfection.
HAV infection is primarily transmitted by the fecal-oral route, by
either person-to-person contact or consumption of contaminated food
or water. Although viremia occurs early in infection and can persist
for several weeks after onset of symptoms, bloodborne transmission of
HAV is uncommon. HAV occasionally might be detected in saliva in experimentally
infected animals, but transmission by saliva has not been demonstrated.
In the United States, nearly half of all reported hepatitis A cases
have no specific risk factor identified. Among adults with identified
risk factors, the majority of cases are among men who have sex with
other men, persons who use illegal drugs, and international travelers.
Because transmission of HAV during sexual activity probably occurs
because of fecal-oral contact, measures typically used to prevent the
transmission of other STDs (e.g., use of condoms) do not prevent HAV
transmission. In addition, efforts to promote good personal hygiene
have not been successful in interrupting outbreaks of hepatitis A. Vaccination
is the most effective means of preventing HAV transmission among persons
at risk for infection. Hepatitis A vaccination is recommended for all
children at age 1 year, for persons who are at increased risk for infection,
for persons who are at increased risk for complications from hepatitis
A, and for any person wishing to obtain immunity.
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