Preliminary evidence for hdv exposure in apparently non-HBV-infected patients.

Hepatitis delta virus (HDV) is a defective human virus that lacks the ability to produce its own envelope proteins and is thus dependent on the presence of a helper virus, which provides its surface proteins to produce infectious particles. Hepatitis B virus (HBV) was so far thought to be the only helper virus described to be associated to HDV. However, recent studies showed that divergent HDV-like viruses can be detected in fishes, birds, amphibians, and invertebrates, without evidence of any HBV-like agent supporting infection.