Hepatitis D is a viral infection that affects the liver and is caused by the Hepatitis D virus (HDV). It can only occur in individuals who are already infected with Hepatitis B virus (HBV), as it requires HBV to replicate. This co-infection can lead to more severe liver disease, including cirrhosis and liver cancer. Transmission of Hepatitis D occurs through contact with infected blood, similar to Hepatitis B. Symptoms may include fatigue, jaundice, and abdominal pain, but some individuals may remain asymptomatic. Vaccination against Hepatitis B can prevent Hepatitis D infection, as the two viruses are linked.