Hepatitis A virus (HAV) is a RNA hepatovirus (in the picornavirus family)
– It is a naked capsid (unenveloped), linear single-stranded, positive-sense RNA virus with a cubic (icosahedral) symmetry
-it replicates in the cytoplasm of the intestinal mucosa by using viral RNA polymerase.
-The virus is transmitted by the fecal-oral route
-More than 90% of adult population is seropositive in developing countries
-The incubation period averages 30 days. it is followed by viremia and spread to the liver and cause lymphoid cell infiltration, necrosis of liver parenchymal cells, and proliferation of Kupffer cells.
-There is no chronic carrier state.
-Risk factors: crowding, poor sanitation,in men who have sex with men, in illicit drug users, and in travelers from the developed countries visiting developing areas of the world.
Symptoms & Signs:
-Contagion is greatest 10 to 14 days before the symptoms appear
-When symptomatic, there is usually fever,malaise, myalgia, arthralgia, easy fatigability, upper respiratory symptoms, a distaste for smoking, anorexia, nausea, right upper quadrant abdominal pain, and jaundice.
-Hepatomegaly, liver tenderness, splenomegaly
-Dark urine and clay-colored stools may be noticed by the patient 1 to 5 days before the onset of clinical jaundice.
-Initial immune response is the development of HAV-specific IgM antibody followed by appearance of IgG after a few weeks. So, the best method for documentation of acute HAV infection is the demonstration of high titers of virus-specific IgM antibody during the acute phase of illness.
-Reverse transcriptase polymerase chain reaction (RT-PCR) can also be used to detect HAV.
-Serum aminotransferases such as ALT and AST as well as bilirubin levels are elevated.
-There is no specific treatment for HAV.
-Supportive measures include adequate nutrition and rest.
-Immune serum globulin (ISG) provides temporary protection if given before or during the incubation period of the disease.
Prevention: an effective inactivated HAV vaccine given in 2 doses 6-12 months apart is recommended for use in children at age 1 and in adults.
-Hepatitis A vaccine prevents postexposure infection
– Almost all cases (99%) of HAV are self-limiting.
-Hepatitis A does not cause chronic liver disease
-IgG-specific antibody is protective
Q: What is the major mode of spread of HAV? by fecal–oral exposure
Q: Why demonstration of IgG antibody is not indicative of recent HAV infection? Because it persists indefinitely
Q: Why do acute hepatitis patients produce dark-colored urine and clay-colored stool? Dark-colored urine is due to excessive bilirubin in urine and clay colored stool is due to lack of drainage of bile salts in the stool through the biliary system due to liver infection.
Q: Why is administration of ISG not indicated when a patient develops clinical symptoms of HAV? Because the patient starts producing antibodies by the time of clinical symptoms.