乙型肝炎病毒感染的自然史

The Natural History of Hepatitis B Infection

研究乙型肝炎 (乙肝 )的自然史对于了解乙肝的发生、发展规律 ,确定预防、治疗乙肝的医学策略均极为重要。目前我国乙肝的传染途径以母婴垂直传播、医源性传播、婴幼儿时期的水平传播为主。乙肝病毒 (HBV)感染后的自然病程可分为 3个时期 ,即免疫耐受期、免疫清除期、病毒低水平复制或无复制期。在免疫清除期 ,乙肝病毒e抗原 (HBeAg)阳性的慢性乙肝表现为病毒复制活跃 ,肝损伤重。如出现了HBeAg血清学转换 ,常伴有病情的缓解。如出现了HBeAg的血清转换 ,但仍有乙肝病毒的活跃复制和肝脏的损伤 ,则病人属HBeAg阴性慢性乙肝。该类病人多有HBV基因的前C区和基础核心启动子的突变 ,治疗效果和预后差。HBeAg阳性和阴性的患者均可转换为乙肝病毒表面抗原非活动性携带状态 ,但这种状态可再度转化为活动性肝病。持续肝脏损伤和HBV持续复制者容易发展为肝硬化。肝硬化的 5年存活率为 5 5 %～ 80 % ,失代偿肝硬化患者的 5年存活率 14 %～ 2 8%。HBsAg有一定的自然转阴率 ,我国约 0 6 %～ 6 6 %。

The research of natural history about hepatitis B is very important for understanding the pattern of incidence,development and progression of hepatitis B,and for making policy of medical decision of prevention and treatment of hepatitis B. At present,the main transmission routes of hepatitis B in our country are still the maternal-infant transmission,nosocomial transmission and horizontal transmission between children under 5 years. The natural history of HBV infection can be divided into three phases: immune tolerance phase,immune clearance phase and low or non-viral replicative phase. In HBeAg + chronic hepatitis B,HBV replicates highly and liver damage is serious. After HBeAg seroconversion,the disease become remission. In some patients with HBeAg seroconversion,there are still active HBV replication and liver damage. They are called HBeAg negative hepatitis B. Gene mutation are commonly seen in pre-C and BCP area in these patients. Both HBeAg positive and negative patients can become inactive carrier state,which indicates a state of low HBV replication with no markedly liver lesion. Persistent liver damage and HBV replication can result in liver cirrhosis. Five-year survival rate of cirrhosis is 55～80%. But in decompensated cirrhosis,the 5 year survival rate is only 14～28%. Some patients can clear HBsAg naturally,and the clearance rate of HBsAg is 0.6～6.6% in China.