Clinical aspects of delta infection.

The clinical features of delta infection were analysed retrospectively in 191 hepatitis B surface antigen (HBsAg) carriers and 592 cases of acute hepatitis B seen over 11 years in the Swedish town of Malmö (population 250 000). With a few exceptions delta infections occurred exclusively in drug addicts. In the chronic HBsAg-carriers the most common clinical manifestation was an episode of acute hepatitis, which in some individuals became severe with a pronounced rise in serum alanine aminotransferase activity for many months. During the period of delta infection the HBsAg titre was lowered and in three out of 26 cases the patient lost HBsAg altogether and developed hepatitis B surface antibodies (anti-HBs). In one patient the acute hepatitis due to delta infection was fulminant and fatal. In patients with acute hepatitis B the clinical picture did not distinguish between those with and without simultaneous delta infection. The frequency with which acute hepatitis B was succeeded by a chronic carrier state was the same whether or not the patient was infected simultaneously with the delta agent. The discovery of the delta agent has improved understanding of the natural history of chronic hepatitis B infection in drug addicts. Thus, instances of acute hepatitis in a chronic carrier, previously termed hepatitis non-A, non-B, may actually be episodes of delta infection.