Hepatitis B :: essays research papers

Risk Factors for HBV Infection Although relatively rare in the United States, hepatitis B is endemic in parts of Asia where hundreds of millions of individuals may be infected. HBV is transmitted horizontally by blood and blood products and sexual transmission. It is also transmitted vertically from mother to infant in the perinatal period which is a major mode of transmission in regions where hepatitis B is endemic. The blood supply in developed countries has been screened for HBV for many years and at present transmission by blood transfusion is extremely rare. Major routes of transmission among adults in Western countries are intravenous drug use and sexual contact. The risk of HBV infection is notably high in promiscuous homosexual men but it is also transmitted sexually from men to women and women to men. Transmission is probably prevented by correct use of condoms. Health care workers and patients receiving hemodialysis are also at increased risk of infection. Effective vaccines are available for the prevention of HBV infection. All individuals at risk for infection should be vaccinated. Post-exposure prophylaxis with hepatitis B immune globulin is also effective for non-immune individuals after a known exposure (e. g. needle stick). Consequences of HBV Infection HBV causes acute and chronic hepatitis. The chances of becoming chronically infected depends upon age. About 90% of infected neonates and 50% of infected young children will become chronically infected. In contrast, only about 5% to 10% of immunocompetent adults infected with HBV develop chronic hepatitis B. In some individuals who become chronically infected, especially neonates and children, the acute infection will not be clinically apparent. Acute hepatitis B can range from subclinical disease to fulminant hepatic failure in about 2% of cases. Many acutely infected individuals develop clinically apparent acute hepatitis with loss of appetite, nausea, vomiting, fever, abdominal pain and jaundice. In cases of fulminant hepatic failure from acute HBV infection, orthotopic liver transplantation can be life-saving. About 90% to 95% of acutely infected adults recover without sequelae. About 5% to 10% of acutely infected adults become chronically infected. The natural history of chronic HBV infection can vary dramatically between individuals. Some will develop a condition commonly referred to as a chronic carrier state. These patients, who are still potentially infectious, have no symptoms and no abnormalities on laboratory testing. Nonetheless, some of these patients will have evidence of hepatitis on liver biopsy. Some individuals with chronic hepatitis B will have clinically insignificant or minimal liver disease and never develop complications.