Chronic viral hepatitis is the principal cause of chronic liver disease, cirrhosis, and hepatocellular carcinoma in the world and now ranks as the chief reason for liver transplantation in adults.¹–³ Of the five known hepatitis viruses, three can cause persistent infection and chronic hepatitis: the hepatitis B virus (HBV),⁴ the hepatitis C virus (HCV),⁵ and the hepatitis delta (or hepatitis D) virus (HDV).⁶ The other two viruses, hepatitis A and hepatitis E, cause acute, self-limited disease only. Recent findings suggest that there is an additional form of viral hepatitis to which two recently discovered human viruses — the hepatitis . . .