Chapter 33 Hepatitis
PATHOPHYSIOLOGY
Hepatitis, or inflammation of the liver, can be caused by a viral agent. Hepatitis viruses can be classified into six types: hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV), hepatitis E virus (HEV), and hepatitis G virus (HGV). The hepatocytes (epithelial cells of the liver) are damaged either directly by the virus or by the body’s immune response to the virus; in either case, there is altered cellular function that leads to inflammation, necrosis, and autolysis of the liver. Regeneration of cells begins when damaged cells are removed by phagocytosis. Usually recovery is achieved with minimal residual damage, although chronic hepatitis and cirrhosis may develop.
Hepatitis A
Hepatitis A is the most highly contagious form of hepatitis and characteristically is an acute, self-limited illness. It is transmitted primarily through the fecal-oral route. It can also be transmitted by unsanitary food handlers, contaminated food supplies, and shellfish from sewage-contaminated waters. It is rarely transmitted through transfusions. Epidemics of hepatitis A have been reported in institutions that house or care for large numbers of children, such as day care centers, schools, and homes for the mentally retarded. The incubation period is approximately 1 month. Jaundice appears 4 to 6 weeks after exposure in older children and adolescents. The disease is transmissible 2 weeks before the onset of jaundice owing to the high concentration of virus in the stool before definitive symptoms are exhibited. The communicable state continues up to 1 week after the onset of jaundice. Hepatitis A manifests a wide spectrum of symptoms and does not lead to chronic hepatitis. Children may have minimal symptoms or be asymptomatic. The child is rarely hospitalized, and there is no known carrier state.
Hepatitis B and Hepatitis C
HBV and HCV are transmitted through blood or blood derivatives and body secretions (wound exudates, semen, saliva, breast milk, urine). HBV can be transmitted perinatally. With the improvement in blood-product screening procedures in recent years, the incidence of transfusion-related infection is decreasing. Hepatitis B occurs most commonly in the following populations of children: (1) infants whose mothers are chronic carriers of the viral antigen HBsAg, (2) children receiving frequent transfusions or hemodialysis (may also develop hepatitis C), (3) children involved in intravenous drug abuse (may also develop hepatitis C), (4) institutionalized children, and (5) children with person-to-person contact with infected individuals. The incubation period for hepatitis B averages 90 days, whereas that for hepatitis C averages 45 days. Children with hepatitis C are typically asymptomatic. In the United States, more than 60% of the cases of hepatitis C are associated with transfusions of blood or blood products. However, an improved blood screening test has greatly reduced the number of new cases. A carrier state and the development of chronic liver disease are possible with hepatitis B and C.
Hepatitis D
HDV can cause infection and clinical manifestations only in association with hepatitis B infection. The virus acts as a parasite of HBV. Coinfection with HDV increases the severity of the HBV infection, creating a more fulminating course and enhancing the potential for chronic liver disease. The incubation period for hepatitis D is 21 to 90 days. Hepatitis D is most common in hemophiliac individuals and intravenous drug abusers.
Hepatitis E
Hepatitis E transmission occurs via the fecal-oral route, primarily via contaminated water, and is often seen after natural disasters in the developing regions of the world. Incubation period averages 40 days for hepatitis E.
Hepatitis G
The primary cause of HGV infection is through transfusion and organ transplantation. Transmitted through blood, this virus has been detected in up to 2% of American blood donors. Infections may persist up to 20 years, with only rare elevation of liver enzyme levels. This type of hepatitis is usually harmless, but more research is needed to determine long-term effects.
INCIDENCE
1. Approximately 90% of young children and infants with hepatitis will not exhibit jaundice.
2. Up to 90% of children younger than 1 year of age, 30% of children 1 to 5 years of age, and 5% of children older than 5 years of age with hepatitis B develop chronic hepatitis.
3. Hepatitis A is the most common type of hepatitis in children. Incidence of hepatitis A is 2.7 cases per 100,000 in the United States (Centers for Disease Control and Prevention, 2005). Incidence has been declining since routine childhood hepatitis A immunization was recommended in 1996. Tropical and developing nations have a higher incidence of hepatitis A than do industrialized and temperate-zone nations.
4. The incidence of hepatitis B in the pediatric population younger than 12 years of age (this group was born after adoption of routine infant immunization for hepatitis B) is 0.02 cases of hepatitis B per 100,000 population in the United States (Centers for Disease Control and Prevention, 2005).
5. Hepatitis C is most common in the adult population and is commonly associated with intravenous (IV) drug use.
