Negatively-stained transmission electron micrograph (TEM) of numerous hepatitis B virus (HBV) virions, also known as Dane particles. HBV contains a genome of DNA, and is a member of the family of viruses known as Hepadnaviridae. It is the cause of a serious disease that attacks the liver, and an infection that can be lifelong, known as cirrhosis (scarring) of the liver, liver cancer, liver failure, and death.