Clinical
Features
Symptoms
The hepatitis A virus has an incubation period of 15 to 20 days
with the average being 28 days. The infection usually does not
last longer than 2 months though there have been reports of prolonged
illness for up to 6 months. Occasionally fulminant hepatitis
A can occur though this is rare. HAV infection does not result
in chronic liver disease or chronic infection.
Symptoms include:
- Fever
- Malaise
- Anorexia
- Nausea
- Abdominal discomfort
- Dark urine
- Jaundice
The clinical definition of hepatitis A is an acute illness with
discrete onset of symptoms, and jaundice or elevated serum aminotransferase
levels. The laboratory diagnosis is a positive anti-HAV IgM regardless
of HbsAg status or significant rise in anti-HAV IgG between acute
and convalescent specimens.
Among children greater than 6 years most infections are asymptomatic
(70%). Older children and adults have symptomatic infection with
jaundice occurring in >70% of patients.
Fulminant Hepatitis A
Fulminant hepatitis A leads to about 100 deaths per year in
the United States. The fatality rate among all reported cases
is approximately 0.3% but can be higher among older persons.
Disease Patterns
Most hepatitis A cases occur in the context of community wide
epidemics in the United States. Such communities are classified
as either high-rate or intermediate-rate.
High-rate communities
In the United States, hepatitis A cases that occur in the context
of community-wide epidemics every 5 to 10 years that last for
several years with substantial rates of disease are considered
high-rate. Case rates can be as high as 700 cases per 100,000
population annually during these outbreaks with few cases among
persons >15 years of age.
Since the hepatitis A vaccine has become available, routine
vaccination of children has been show to be feasible in these
communities.
Intermediate-rate communities
In the United States, hepatitis A cases that occur primarily
among children, adolescents, and young adults with epidemics
occurring at regular intervals and persisting for several years
are considered intermediate-rate. Case rates are between 50 and
200 cases per 100,000 population per year. Often cases are concentrated
in specific neighborhoods within a larger community. During these
community-wide outbreaks, children with asymptomatic HAV infection
can be a source of infection for older persons.
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