Hepatitis A 

The differential diagnosis of infectious hepatitis includes infection with 

• hepatitis A, B, D (delta)

• non-A, non-B (C, E) viruses

• Epstein-Barr virus 

• cytomegalovirus

• toxoplasmosis

• leptospirosis

• secondary syphilis. 

The differential diagnosis of  noninfectious hepatitis

• drug-induced

• alcoholic hepatitis

• cirrhosis

• hepatic tumor

• abscess 

Etiology:

•  HAV is a single-stranded RNA virus belonging to the picornavirus group.

  • It can survive readily in a variety of environments, including seawater.

Life cycle of the virus

Clinical Manifestations:

• The incubation period is 2-8 weeks

• Hepatitis A characteristically is an acute selflimited illness associated with fever, malaise, jaundice, anorexia, and nausea. 

• Symptomatic hepatitis occurs in approximately 30% of infected children younger than 6 years of age; few of these children will have jaundice.

• Among older children and adults, infection usually is symptomatic and typically lasts several weeks, with jaundice occurring in approximately 70%.

• Prolonged or relapsing disease lasting as long as 6 months can occur. 

• Fulminant hepatitis is rare but is more frequent in persons with underlying liver disease. 

• Chronic infection does not occur unlike HBV

• No increased risk for hepatic carcinoma unlike HBV

• Recovery is generally complete with lasting immunity

Epidemiology:

• Trasmission

  • The most common mode of transmission is person-to-person, resulting from fecal contamination and oral ingestion, ie, the fecal-oral route. Eating raw oysters harvested from fecally contaminated water. Filter-feeding shelfish, such as oysters, clams and mussels are believed to concentrate the virus.

  • In most infected persons, the highest titers of HAV in stool occur during the 1 to 2 weeks before the onset of illness, when patients are most likely to transmit HAV. 

  • Common-source foodborne outbreaks occur

• People at risk

  • A close personal contact with a person infected with hepatitis A

  • household or personal contact with a child care center

  • international travel

  • a recognized foodborne 

  • waterborne outbreak

  • male homosexual activity

  • use of injection drugs

•  In developing countries, where infection is endemic, most persons are infected during the first decade of life; in developed countries, infection may occur at an older age.

Diagnostic Tests:

• Serologic tests for HAV-specific total and immunoglobulin (Ig) M antibody are available. 

  • Serum IgM is present at the onset of illness and usually disappears within 4 months but may persist for 6 months or longer.

  • Presence of serum IgM indicates current or recent infection

  • The presence of IgG antibodies to -HAV without IgM indicates past infection and immunity.

• Virus is not cultivable. Direct detection by immunologic or EM not widely available

Treatment:

• Supportive

• Isolation of the Hospitalized Patient

  • In addition to standard precautions, contact precautions are recommended for diapered and incontinent patients 

  • The major methods for prevention of HAV infections are improved sanitation and personal hygiene

  • Children and adults with acute HAV infection who work as food handlers or attend or work in child care settings should be excluded for 1 week after onset of the illness.

• Prevention

  Factors to consider in choosing active and/or passive prophylaxis include the interval before departure, the relative costs and availability of IG and hepatitis A vaccine, the duration of the stay, and the likelihood of repeated exposure during subsequent travel 

   

  • Immune Globulin.

    • Immune Globulin (IG), when given within 2 weeks after exposure to HAV, is greater than 85% effective in preventing symptomatic infection. 

    • To travellers to high endemic areas

      • Protection lasts for 6 months. To be repeated if staying longer.

  • Hepatitis A Vaccine 

    Two inactivated hepatitis A vaccines currently are available in the United States. Immune globulin is considered protective against hepatitis A immediately after administration, whereas the precise time required from receiving 1 dose of vaccine to onset of protection has not been established but likely requires 2 to 4 weeks.

    • Efficacy.

      • In double-blind, controlled, randomized trials, the protective efficacy in preventing clinical hepatitis A was 94% to 100%.

    • Duration of Protection.

      • The need for booster doses cannot be determined because hepatitis A vaccines have been under evaluation for only a short time.

    • Who to administer

      • International travellers to endemic areas

      • Children who live in endemic areas

      • Homosexual men

      • Food handlers

      • To a community to control an outbreak

  • General measures:  Eat only adequately cooked seafood. The virus is inactivated by boiling for 1 munute.