Hepatitis A Virus is a naked, positive-sense single-stranded
RNA virus with an icosahedral capsule. It is classified as a picornavirus.
HAV is spread primarily by a fecal-oral route. It can
survive outside the body for months and is highly stable, resistant to
detergents, acid, and high temperatures. Outbreaks generally occur from a
single source as there is a long asymptomatic period of high viral shedding. It
is more common in conditions of overcrowding or poor hygiene. Additional
persons-at-risk include travelers to endemic regions, intravenous drug users,
and MSM populations.
After being acquired via ingestion, HAV penetrates through
the lining of the gastrointestinal tract to reach the blood, which carries it
to the liver. It binds and enters hepatocytes and Kupffer cells via the HAC
cell receptor 1 glycoprotein. After replicating, it is released from the cells
via exocytosis (it does not lyse infected cells). There is no chronic infection
Prior infection with Hepatitis A confers protection against reinfection
Symptoms are caused via immune-mediated damage to the liver.
Initial symptoms include fever, fatigue, nausea, loss of appetite, vomiting and
abdominal pain. Dark urine, pale stool and jaundice may follow. While jaundice
is observed in 70% to 80% of adults, it is observed in only 10% of cases
Generally is self-limited course. Hepatitis A does not lead to chronic infection
Diagnosis can be made based on a specific serological test,
and may be supplemented by clinical symptoms, identification of the known
infection source. Serology is done via enzyme-linked immunosorbent assay
(ELISA) directed towards anti-HAV IgM.
consisting of immune serum globulin may be given up to 2 weeks after the
exposure in order to prevent the clinical illness. Cell-mediated immunity (NK cells and
cytotoxic T-cells) are needed to clear the infection by eliminating infect
Post-exposure prophylaxis can be attained by administering serum immune globulin, or (preferably) vaccine.
A vaccine of killed HAV is recommended for all children as
well as adults who are at high risk for infection. It is administered in two
doses, 6 months apart, generally concurrently with the HBV vaccine.