Hepadnaviruses can cause liver infections in humans and animals. The two recognized genera are Genus Orthohepadnavirus and Genus Avihepadnavirus. It has a small genome of partially double-stranded, partially single stranded circular DNA. It is a group 7 virus that uses an RNA intermediate during replication.

Most people who come into contact with the virus are able to clear the infection alone although some cannot and usually progress to fulminant hepatitis. It can cause sever liver damage and in rare cases may lead to hepatocellular carcinoma. Treatment is very expensive and can last for 12-15 weeks and makes the patient very sick. The interferon treatment tries to kick-start the host immune response to clear the infection.