New epidemiology of hepatitis delta.

Hepatitis D virus (HDV) is a defective pathogen that needs hepatitis B virus (HBV) for infection. Co-infection of HBsAg-positive individuals with HDV is commonly associated with a more rapid progression to cirrhosis, a higher incidence of hepatocellular carcinoma (HCC) and increased mortality. Initial studies have shown that about 5% of chronic HBV carriers worldwide (15-20 millions) were also infected with HDV. However, recent studies suggest that the prevalence of HDV is at least two- to three-fold higher than previous estimations. Improved diagnostic techniques have shown that HDV infection remains endemic in certain areas of the world. Injection drug users, individuals with high-risk sexual behaviour and patients co-infected with human immunodeficiency virus (HIV) represent the major reservoir of the disease in the Western world. Although the burden of HDV infection significantly decreased in Europe in the nineties, there has been no further decrease in the last decade, probably because of migration from HDV endemic countries. Until new and more effective therapies are available, public health measures should be reinforced by increasing prophylactic HBV vaccination programs, preventing transmission of the virus among parenteral drug users and implementing universal HDV screening of all HBV-infected individuals.