title: Avihepadnavirus
text: # Avihepadnavirus
  
  Avihepadnavirus is a genus of viruses, in the family Hepadnaviridae. Birds serve as natural hosts. There are three species in this genus. Diseases associated with this genus include: hepatitis, hepatocellular carcinomas (chronic infections), and cirrhosis.
  
  ## Taxonomy
  
  The genus contains the following species:
  
  * Duck hepatitis B virus
  * Heron hepatitis B virus
  * Parrot hepatitis B virus
  
  ## Structure
  
  Viruses in the genus Avihepadnavirus are enveloped, with spherical geometries, and T=4 symmetry. The diameter is around 42 nm. Genomes are circular, around 3.2kb in length. The genome codes for 7 proteins.
  
  | Genus | Structure | Symmetry | Capsid | Genomic arrangement | Genomic segmentation |
  | - | - | - | - | - | - |
  | Avihepadnavirus | Icosahedral | T=4 | Non-enveloped | Circular | Monopartite |
  
  ## Life cycle
  
  Viral replication is nucleo-cytoplasmic. Replication follows the dsDNA(RT) replication model. DNA-templated transcription, specifically dsDNA-RT transcription, with some alternative splicing mechanism is the method of transcription. Translation takes place by ribosomal shunting. The virus exits the host cell by budding, and nuclear pore export. Birds serve as the natural host. Transmission routes are parental, sexual, and blood.
  
  | Genus | Host details | Tissue tropism | Entry details | Release details | Replication site | Assembly site | Transmission |
  | - | - | - | - | - | - | - | - |
  | Avihepadnavirus | Birds | Hepatocytes | Cell receptor endocytosis | Budding | Nucleus | Cytoplasm | Vertical: parental; sex; blood |
  