Viral Hepatitis in Taiwan: Status in the 1990s

Abstract

Until fairly recently, hepatitis A virus (HAV) and hepatitis B virus (HBV) infections were endemic to Taiwan. Since the start of a national hepatitis control program in 1981 and the launch of a national HBV vaccination program in 1984 HAV and HBV infections have decreased remarkably. Currently, less than 5% of children below age 15 are seropositive for anti-HAV or hepatitis B surface antigen (HBsAg). However, there are still large numbers of HBsAg carriers, and new cases of hepatitis, including acute hepatitis D virus (HDV) infection, continue to occur in the adult population. A recent study conducted in our unit comparing these figures with data from the 1980s showed that the proportion of acute hepatitis B and non-A, non-B had increased and that acute hepatitis in previously unrecognized chronic HBsAg carriers had decreased significantly. While the majority of non-A, non-B hepatitis cases were type C hepatitis, 10% and 20% were sporadic hepatitis E and non-A, non-B, non-C, non-D, non-E, respectively. The etiology of chronic liver diseases remained unchanged, with 75%–80% being HBsAg positive. Of the patients with chronic viral hepatitis, 17% had dual viral infections (HBV+HDV or HBV+HCV) and 1% had triple viral infections (HBV+HCV+HDV). Among patients with chronic viral hepatitis of various etiologies, the clinical course is similar in that acute exacerbation frequently occurs and cirrhosis as well as hepatocellular carcinoma may develop. In dual or triple hepatitis viral infections, HCV may suppress HBV or HDV and lead to HBsAg clearance or even take over the role of HBV in causing persistent hepatitis. While mass vaccination and education are effective for HAV, HBV, HDV, and HEV prevention, and interferons are available for the treatment of chronic viral infections, further studies are needed to control the progression of existing chronic liver diseases and the spread of HCV.