Hepatitis D infection occurs only in the presence of infection with which virus?

• A. Hepatitis A
• B. Hepatitis B
• C. Hepatitis C
• D. Hepatitis E

Answer: (B)

Hepatitis D is a defective satellite virus that can only replicate and cause infection in the presence of hepatitis B virus. It relies on the hepatitis B surface antigen (HBsAg) from an HBV infection to form its outer envelope, so HDV cannot establish infection on its own. Therefore, hepatitis D occurs only in people who are infected with hepatitis B (either as a co-infection or as a superinfection in someone with chronic HBV). Vaccination against hepatitis B helps prevent hepatitis D by eliminating the HBV component needed for HDV to propagate. Transmission mirrors that of HBV, through blood and sexual routes, as well as perinatal exposure.