Читать книгу Assisted Reproduction Techniques - Группа авторов - Страница 42

Hepatitis B virus (HBV), a DNA virus, is the most common chronic viral infection in the world, having infected approximately 2 billion people [1]. It is estimated that there are more than 350 million people who are chronic carriers of HBV and that the virus causes approximately 786,000 deaths per year. HBV‐related death is caused by chronic hepatic inflammation leading to chronic liver failure, cirrhosis and hepatocellular cancer. HBV vaccination programs are safe and effective. However, global prevalence of HBV is highly variable due to differences in the uptake of universal HBV vaccination programs [2].

HBV is transmitted through contact with infected blood or semen. Where HBV prevalence is high, the most common route of transmission is vertical, from infected mother to neonates. Where HBV prevalence is low, the commonest mode of transmission is through sexual contact. HBV can also be transmitted by blood transfusion, renal dialysis or unsafe use of needles for drug injection [3].

The risk of developing chronic infection is age dependent. In neonatal transmission, the risk of chronic liver disease is 95%. If transmitted in childhood, the chance of chronic liver disease is 80%. If infected in adulthood, the chance of chronic liver disease is 5% [4].

The diagnosis of HBV infection is made by serological testing. HBV surface antigen (HBsAg) is diagnostic of acute and chronic infection. Positive HBsAg indicates that the patient is infective. Two weeks after acute infection, hepatitis B core antibody (anti‐HBc) IgG becomes positive by serological testing, and the infected patient will have raised liver transaminase activity and also become symptomatic (flu‐like symptoms, loss of appetite, diarrhea, vomiting and jaundice). During recovery from acute infection or after successful vaccination, hepatitis B surface antibodies (anti‐HBs) appear. Clinical interpretation of the serological markers of HBV infection should be made with all available serological test results (table 5.1) [1].