熟读理解课文,完成 Tasks 1 Text A Hepatitis B Hepatitis is an inflammation of the liver. It may be caused by drugs, alcohol use, or certain medical conditions. But in most cases, it's caused by a virus that infects the liver. This is known as viral hepatitis, and the most common forms are hepatitis A, B, and C. Hepatitis B is a major global health problem and the most serious type of viral hepatitis. When someone is exposed to the hepatitis B virus (HBV), there are two types of infections, acute infection or chronic infection. Acute hepatitis B occurs during the first one to four months after acquiring the virus. Acute hepatitis B can be symptomatic or asymptomatic. Most young children and fewer than half of adults with acute hepatitis B never experience any symptoms. Only 30% to 50% of adults develop significant symptoms during acute infection. Early symptoms of acute hepatitis B may include: nausea, vomiting, loss of appetite, fatigue, body aches, jaundice and dark urine. Most people can get rid of the virus within 6 months. Less than one percent of the people infected with acute hepatitis B die due to liver damage in this early stage Around 10% of the infected people develop a chronic, life-long HBV infection. Having chronic hepatitis B dramatically increases your chance of permanent liver damage, including cirrhosis and liver cancer. To determine if an infection is chronic or acute, a blood sample may be taken and analyzed for Hepatitis B surface antigen, Hepatitis B core antibody, Hepatitis B surface antibody. HBsAg (hepatitis B surface antigen) : This tests for the presence of virus. A positive test result indicates that the person may have a hepatitis B infection. If the virus is present for more than six months, a person is considered to be chronically infected. HBsAb or Anti-HBs (hepatitis B surface antibody) : A positive test result indicates that a person has successfully responded to the hepatitis B vaccine or has recovered from an acute hepatitis B infection. This result means that the person is immune to future hepatitis B infection. HBcAb or anti-HBc (hepatitis B core antibody) : The interpretation of the positive test result depends on the results of the above two tests. Its appearance with positive HBsAb or anti-HBs indicates that the person may have been already vaccinated or he has recovered from a prior hepatitis B infection. For chronically infected persons, it will usually appear with the positive HBsAg. When a person has acute hepatitis B, the doctor may also test the blood for a certain liver enzyme called ALT that is released by liver cells when they are inflamed, damaged or die. When this enzyme is present at high levels, it means that liver damage is occurring as the immune system is trying to kill infected liver cells. People who have chronic HBV infection need regular monitoring of their liver condition to determine whether their disease is progressing, whether treatment is needed, or whether a liver cancer is developing. For example: a low level of blood albumin indicates some form of liver disease, such as hepatitis, or cancer in the liver. Prolonged prothrombin time is a valuable early indicator of liver damage. HBV is transmitted through contact with infected blood or other infected bodily fluids, through unprotected sex, unsterilized needles, and from an infected mother to her newborn during the delivery process. HBV is not transmitted casually, through the air, or from casual social contact (hugging, coughing, sneezing). Ways to reduce your risk of HBV include : 1.Get vaccinated against hepatitis B. 2.Wear gloves and dispose of syringes properly if you are a person who works with blood at your job. 3.Practice safe sex and use condoms, especially if your partner carries (or is at high risk for) hepatitis B. 4.Avoid sharing foods with infected people , especially foods that involve a high potential for saliva exchange (such as chewing gum and drinks) 5.Avoid sharing certain personal items, such as razors and toothbrushes. Task1 Answer the following questions according to Text A. 1. Whatare the possible symptoms caused by acute hepatitis B? 2. Whatare people suffering from chronic hepatitis B likely to develop? 3. How can people tell acute hepatitis B from chronic hepatitis B? 4. Why do people who have chronic HBV infection need regular monitoring of theirliver condition? 5. How is HBV transmitted?