“Hepatitis D is a liver infection caused by HDV. HDV is known as a “satellite virus” because it can only infect people who are also infected by the hepatitis B virus (HBV). HDV can cause severe symptoms and serious illness that can lead to liver damage and even death.

Because hepatitis D is not a nationally notifiable condition, the actual number of hepatitis D cases in the US is unknown.

People with hepatitis D can become infected with both HBV and HDV at the same time or get hepatitis D after first being infected with HBV. These two types of HDV infection are defined below.

People who get infected with both HBV and HDV at the same time are considered coinfected. Coinfection with HBV and HDV can cause serious short-term health problems and even liver failure, but it usually does not lead to lifelong illness.

Superinfection happens when people get hepatitis D after first having been infected with HBV. This type of infection is more likely to result in long-term illness, including rapid development of liver fibrosis, liver failure, and even death.”