What is required for Hepatitis D to occur?

Hepatitis D is unique because it is a satellite virus that cannot replicate on its own. It requires the presence of Hepatitis B virus (HBV) for its infection cycle. The reason behind this synergy is that Hepatitis D virus (HDV) uses the proteins produced by Hepatitis B for its own viral envelope. Therefore, an individual must be infected with Hepatitis B first to then contract Hepatitis D. This requirement distinguishes Hepatitis D from other hepatitis viruses, as it is dependent on the presence of another virus to cause disease.

The other options, such as previous infections with Hepatitis A or C, do not directly relate to the necessity for Hepatitis D to occur. While direct contact with infected blood is a common way for various bloodborne pathogens to spread, it does not specifically lead to the ability of Hepatitis D to exist without Hepatitis B. This connection to Hepatitis B is essential for understanding the interactions between viruses and how co-infections can affect treatment and management of liver diseases.