Orthohepadnavirus

The Orthohepadnavirus genus belongs to the Hepadnaviridae family of viruses. These viruses are characterized by their small, enveloped, spherical structure, approximately 40–48 nm in diameter. Their capsid contains a circular double-stranded DNA molecule with a single-stranded region and a DNA-dependent DNA polymerase enzyme essential for replication. A key feature of hepadnaviruses is their use of reverse transcriptase for replication and the abundance of hepatitis B surface antigen (HBsAg).1

The Orthohepadnavirus genus specifically includes hepatitis B viruses that infect mammals, such as humans, woodchucks, and woolly monkeys. The other genus within Hepadnaviridae is Avihepadnavirus, which infects birds.1

Infection with hepatitis B virus can lead to severe liver disease, known as hepatitis. While it can be acute, in about 5-10% of human cases, it becomes chronic, potentially causing permanent liver damage. Symptoms typically appear 40 days to 6 months after exposure. A vaccine is available for protection, and passive immunization can also be used. Individuals who carry the hepatitis B virus are at a significantly higher risk of developing liver cancer.1