Hepatitis A Virus, HAV

Sample

1. Venous blood is needed to prepare the serum.
2. A random sample can be used.
3. The serum can be stored at 4 °C for 5 days.
4. Feces can be taken for immuno-electron microscopy.

Purpose of the test

• To diagnose viral hepatitis A (HAV) infection.

Pathophysiology

1. 1. Hepatitis A viral infection is also called Infectious hepatitis.
   2. Hepatitis virus A is a non enveloped virus that belonged to the hepatotropic virus family and is 27 nm in diameter.
      1. HAV belongs to the Picornaviridae family.
         1. The is a picornavirus.
         2. Genus is a hapatovirus.
   3. Structure of the virus:
      1. It consists of a single-stranded RNA virus (ssRNA).
      2. VPg is a Viral protein genome-linked. This is a protein attached to the positive strand of viral RNA.
         1. VPg acts as a primer during the RNA synthesis.

1. 3. HAV is a self-limiting acute liver disease.
   4. The incubation period is short which is 2 to 6 weeks.
   5. This is a highly contagious of viral infection and most common in children.
      1. Most children recover from the disease and develop lifelong immunity.

Mode of spread:

1. 1. 1. Inactive stage, this virus is excreted in the stool.
      2. So there is an oro-fecal spread because of the contamination of food and drinks.
      3. Sexual transmission between male homosexuals has been reported.
      4. Transmission via blood transfusion and I/V drug use is rare.

Clinical course:

1. 1. 1. Mostly asymptomatic.
      2. The most common age group is children.
      3. There may be a prodromal period of fever, chills, fatigue, malaise, and headache.
         1. The above symptoms will be followed by nausea and vomiting.
      4. There is anorexia.
      5. Sometime there may be abdominal pain which is usually in the upper quadrant.
      6. Sometime there may be gastroenteritis.
      7. When jaundice appears then there is rapid improvement in the clinical symptoms.

Outcome HAV infection:

1. There is mild to severe disease.
2. Mostly recovered from the HAV infection and gets life-long immunity.
3. Very few die of HAV infection with fulminant hepatitis.

High-risk group:

1. Children care centers.
2. The family members who are in close contact with the patient.
3. In the summer camps.
4. People working in correctional centers.
5. In homosexual peoples.

Immunology:

1. 1. 1. The first antibody in acute infection is IgM type (HAV-IgM)
      2. IgM appears 3 to 4 weeks after the exposure to the virus or just before the liver function tests are raised.
         1. IgM returns to normal in roughly 8 weeks, or disappear in 3 to 4 months.
      3. HAV-IgG appears after 2 weeks when IgM is increasing.
         1. Now IgM slowly comes to normal and IgG will be present in the blood.
         2. HAV-IgG will be detectable in the blood even after 10 years.

      4. Disease stage	IgM	IgG
         Acute infection	Positive	Negative
         Later on	Positive	Positive
         Immunity	Negative	Positive

Diagnosis:

1. 1. 1. HAV-IgM indicates acute infection.
      2. HAV-IgG positive and HAV-IgM negative indicate convalescent or chronic stage.
         1. HAV total antibody indicate present or past infection.
         2. HAV total antibody also indicate vaccination.
      3. PCR: In the early stage antibodies are not detectable then only PCR for RNA can be found in the stool and blood. PCR for RNA may be found in the saliva as well.
      4. Fecal HAV is positive 2 weeks before the symptoms appear.

 

Prevention:

1. The best is to give the vaccine in epidemic areas and to the children.
2. Improve:
   1. Safe water supply.
   2. Safe food supply, which is the best hygienically.
   3. Have good sanitation.
   4. Washing of the hands before taking the foods.

Treatment:

1. 1. • These patients recover without any treatment.
      • Mainly there is a need for supportive treatment.

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