Hepatitis B Virus and the Carrier Problem

Abstract

Hepatitis B Virus and the Carrier Problem* Baruch S. Blumberg (bio) this conference is dedicated to the notion that we are children of history and can learn about the future by studying the past. This process also teaches us that we usually don't do so; but that shouldn't deter us from examining the history of disease in order to find directions for contemporary health problems—for example, the current tragic epidemic of AIDS. My plan today is to discuss the experience with a worldwide pandemic of infection with the hepatitis B virus (HBV), starting from about the time that the virus was identified.1 Many of the same ethical, social, psychological, and research problems that have arisen with other infectious disease epidemics have been encountered with HBV, but each has a character of its own. I'll attempt to point out some of these problems as they apply to AIDS and other diseases as the narrative unfolds. HBV AND HIV HBV has many similarities to the virus that is considered to be the cause of AIDS, the human immunodeficiency virus (HIV). HIV is an RNA retrovirus, one that replicates using a step in which the RNA of the virus makes DNA using the enzyme reverse transcriptase to do so. HBV is classified as a DNA virus. However, in its replication process, HBV also utilizes a reverse transcriptase to make DNA from RNA. In addition, HBV has epidemiologic characteristics in common with HIV. Many of the groups that are at high risk for infection with HIV are also at risk for HBV: male homosexuals, transfused patients and patients [End Page 377] who receive certain blood products (e.g., hemophilia patients), drug abusers, the newborn children of infected mothers, and certain populations in Africa. There are, however, exceptions. For example, HBV infection is very common in China, Japan, India, and other countries in Asia, but HIV is rare. HBV has an affinity for the liver; it can seriously impair liver function and lead to yellow jaundice, the most striking finding in the disease. Many cases result in an acute disease which can be disabling but usually progresses to a complete recovery. Some acute cases, however, develop chronic infection and chronic liver disease which can cause disability and shorten life expectancy. In addition, many people are occultly infected with HBV and become chronic carriers of the virus. There are estimated to be about 200 million carriers of HBV in the world, most of them in Africa and Asia. There are about 1 million carriers in the United States. Carriers remain asymptomatic for many years, but some will eventually suffer from chronic liver disease and, particularly in Asia and Africa, are at relatively high risk for the development of primary cancer of the liver. In these regions, cancer of the liver is one of the most common cancers and a problem of publichealth proportions. There are important differences between HIV and HBV. HBV has been around for a long time; it may have been noted in the Egyptian and Indian Ayurvedic texts and in the Babylonian Talmud. Many indigenous medical systems contain remedies for the treatment of jaundice, some of which was probably due to HBV infection. HIV, on the other hand, appears to have been introduced recently—perhaps in the 1970s—and was rare until the present decade. The diseases are perceived differently by the public; because of its high fatality rate, AIDS is far more feared. However, worldwide, more people are made ill or die as a consequence of HBV infection. Another important difference is that there is a very effective and safe vaccine to prevent infection with HBV; at present, none is available for HIV. [End Page 378] DISCOVERY OF HEPATITIS B VIRUS In the mid 1960s, we discovered that HBV could be detected in blood by the use of a reactant present in the blood of patients who had received large numbers of transfusions. Apparently, some transfusion units had contained HBV, and the patients had developed an antibody against it which could be used to detect the virus in other people's blood. By a strange irony, the blood of people who had already been exposed to the...