What requirement is necessary for Hepatitis D virus to infect?

Hepatitis D virus (HDV) has a unique requirement for infection: it can only infect individuals who are already infected with Hepatitis B virus (HBV). This is because HDV is a satellite virus that relies on the surface antigens of HBV for its own replication and assembly. Without the presence of Hepatitis B, HDV cannot propagate within the host, making previous Hepatitis B infection a prerequisite for HDV infection.

The Hepatitis D virus utilizes the envelopes derived from Hepatitis B to create its own viral particles, which further illustrates the dependence of HDV on HBV. Therefore, only those who are already infected with Hepatitis B can subsequently become infected with Hepatitis D. This interplay is critical in understanding the co-infection dynamics and treatment challenges faced by patients with both viruses.