Delta hepatitis in inapparent carriers of hepatitis B surface antigen

Infection with the hepatitis B surface antigen (HBsAg)-associated delta agent (δ) was determined in a series of Italian patients with a diagnosis of acute hepatitis B (HBsAg-positive) progressive to chronicity. Twenty-two of 27 (81%) and 12 of 18 (67%) patients collected, respectively, in Naples and Cagliari, where δ is highly endemic, developed immunoglobulin M antibody to δ and/or rising titers of immunoglobulin G anti-δ during the initial acute phase of the disease. In each of them, anti-δ increased to a high-titered plateau indicative of chronic δ infection. Delta markers were found in none of the 13 patients collected in Siena, where the prevalence of δ infection is low. The great majority of the patients with anti-δ and a progressive form of HBsAg-positive hepatitis lacked the IgM antibody to hepatitis B core antigen. They were presumably unrecognized carriers of HBsAg who became infected by δ and developed hepatitis induced by this agent. In areas where δ is endemic, it may represent the true cause of seemingly type B hepatitis progressing to chronic HBsAg-positive liver disease.