Hepatitis B virus (HBV) is a DNA virus that infects mainly the liver cells in a human body and becomes incorporated into the human DNA inside their nuclei (pleural of nucleus).
Expert: Andy S. Yu, MD, Gastroenterology
- What is hepatitis B? What are the symptoms if you are infected with hepatitis B?
- Hepatitis B virus (HBV) 乙型肝炎病毒 is a DNA virus that infects mainly the liver cells in a human body and becomes incorporated into the human DNA inside their nuclei (pleural of nucleus). Hepat- stands for liver and –itis stands for inflammation (發炎). Hence hepatitis (肝炎) is the inflammation of the liver, which could be due to one or few of many multiple causes, and hepatitis B is the inflammation of the liver in response to the infection (感炎) by HBV.
- Hepatitis B presents just like any type of hepatitis, with a combination of inflammation and fibrosis (纖維化), and a clinical spectrum from asymptomatic state (無症狀態), nonspecific symptomatology of fatigue and anorexia, to extreme cases of liver failure (肝臟衰竭) as characterized by jaundice (黃膽), ascites (腹水), portal hypertension (門脈高壓) with severe gastrointestinal bleeding, hepatic encephalopathy (肝腦症) with confusion and even coma, kidney failure (腎臟衰竭), and death. HBV may also lead to liver cancer, independent of the severity of patient’s liver inflammation or fibrosis.
- How is hepatitis B transmitted?
Dr. Yu: HBV can be transmitted essentially via any body fluids, with the high concentrations of viral particles in blood and wound exudates; low concentrations in stool, urine, sweat, and breast milk; and intermediate concentrations in semen, vaginal fluid, and saliva. The most common route of transmission among Asians is vertical, i.e., from mother to newborn baby during bloody delivery. Other common routes of transmission include contaminated needles, other healthcare utensils, and blood products; acupuncture, body and ear piercing, tattoo; recreational drugs such as injection drug abuse and intranasal cocaine; and household contaminations such as sharing of toothbrushes, dental floss, razor blades, and nail clippers. The most common mode of transmission in the Western world is sexual contact.
- What are prevalence rate of hepatitis B in general population and Chinese population?
Dr. Yu: The prevalences of HBsAg carriers (乙型肝炎帶原者) in the world and in the US are near 300 million and 2.4 million, with annual mortality rate of 1 million and 3,000 cases, respectively. On the other hand, Asians occupy 4.5% of the entire US population, with > 15% of Asians carrying HBsAg (表面抗原). Yet > 50% of American carriers of HBsAg are Asians, with > two-thirds of these infected Asian Americans unaware of their infection.
- Why hepatitis B is so prevalent in Chinese population?
Dr. Yu: As above, the most common route of HBV infections among the Chinese is vertical, i.e., from mother to newborn baby during bloody delivery. (Of course, any delivery, whether vaginal or Cesarean section, cannot be nonbloody.) A fertile woman in her relatively young childbearing age is in an age range when the HBV is much more replicative, the viral level is the highest, and her body fluid is most infectious. A newborn baby, from the time of his/her birth to 5 years of age, is the time when the body has the weakest immune response, thus the most impaired ability to ward off the virus or to deter viral replication. Hence we are talking about the transmission of virus from a very replicative and highly concentrated source as the mother to a very receptive and vulnerable victim as the baby.
- What are the risks if hepatitis B is not diagnosed, monitored or treated?
Dr. Yu: HBV is a silent killer. Without a prompt diagnosis, the undiagnosed carrier may enjoy years of asymptomatic state, but miss the window opportunity for effective therapy, and develop finally symptoms at a late stage of the disease, such as cirrhosis (肝臟硬化) or extreme fibrosis; liver failure; or liver cancer.
- What is the link between hepatitis B and liver cancer?
Dr. Yu: HBV is a carcinogenic virus that may cause cancer even in the absence of any liver inflammation or fibrosis. On the other hand, for those patients who have lost the HBsAg, thus achieving a convalescent state or remission (緩和狀態) the viral particles remain dormant in the human genome or nucleus of the liver cells, thus predisposing to liver cancer at a lower (compared with those with positive HBsAg) but still finite risk, approximating 0.55% annually.
- How many percentage of liver cancer cases that are caused by hepatitis B?
Dr. Yu: HBV contributes to 50 – 55% of all liver cancers in the world, but only 15 – 20% in the United States. In the US, 45 – 50% of liver cancers are due to chronic hepatitis C and the remaining 35% are due to nonviral cause.
- What are the prevalence and mortality rate of liver cancer in Chinese population?
Dr. Yu: 85% of all liver cancers originate from Asia and Africa, with annual incidence of 780,000 cases in the world and only 42,000 in the US, leading to annual mortalities of 750,000 cases and 30,000 cases, respectively.
- Are there warning signs or symptoms for liver cancer?
Dr. Yu: Early stage of liver cancer can usually be detected by routine screening methods but is mainly asymptomatic or nonspecifically symptomatic, e.g., fatigue or anorexia, at this early stage. The patient would be at a very advanced age by the time when significant symptoms have evolved, including severe presentations such as abdominal pain, jaundice, liver failure (ascites, hepatic encephalopathy, gastrointestinal bleed); local lymph node or nearby organ metastases; or distant metastases such as lung or bone.
- Is hepatitis B preventable? How?
Dr. Yu: Hepatitis B is best preventable by vaccination, especially to newborn babies within 12 hours of their delivery by commencing the usual vaccine program (1st shot now, 2nd shot at 1 month, and 3rd shot at 6 months). For babies born to HBV-infected mothers, they should also be given concomitantly as additional measure, within 1st 12 hours of their delivery, hepatitis B immune globulin (HBIg) 免疫蛋日. All other Asians should be tested for hepatitis B by blood examination and if the results are all negative, should be administered HBV vaccine too. In addition, contact precautions should be exercised for all individuals, including protective sex, covering all wounds as HBV particles may remain viable and infectious outside one’s body for over 7 days, and no sharing of toothbrushes, dental floss, razor blades, and nail clippers.
- How do I know if I am infected with hepatitis B?
Dr. Yu: All Asians, and Chinese, should be tested for HBsAg, anti-HBc (核心抗體), and anti-HBs (表面抗體), with results submitted to their doctors for interpretation. HBsAg carriers, plus those who have achieved convalescence, may not have any abnormalities in their usual annual liver blood tests, including serum aminotransferases. There are official guidelines from various healthcare societies that include other patient groups, including pregnant women, high-risk populations (men having sex with men, intravenous drug users, HIV infected) and other immunocompromised patients, for the purpose of HBV testing.
- For those who are chronically infected by hepatitis B, how can they prevent themselves from liver cancer?
Dr. Yu: The use of antiviral therapy, with the objective to suppress viral replication, can minimize the risk of liver cancer. On the other hand, routine screening, in the form of semiannual liver ultrasound (超音玻) and AFP (甲胎蛋日血液檢查), will allow liver cancer to be detected in a much earlier and treatable (可治療, 並不代表可治愈), if not curable (治愈), state.