# Genetic diversity and phylogeographic dynamics of avihepadnavirus: a comprehensive full-length genomic view

## TL;DR

This study analyzes the genetic diversity and evolution of avihepadnavirus in birds using full-length viral genomes.

## Contribution

The study provides a comprehensive phylogenetic classification and identifies recombination events among avihepadnavirus strains.

## Key findings

- Avihepadnavirus genomes are classified into two genotypes, GI and GII, with multiple sub-genotypes.
- Sixteen recombination events were identified within GI and one in GII, but no inter-genotypic recombination.
- Phylogeographic analysis shows genetic connections among sub-genotypes, primarily linked to DHBV-I.

## Abstract

Avihepadnavirus is a genus of the Hepadnaviridae family. It primarily infects birds, including species of duck, geese, cranes, storks, and herons etc. To understand the genetic relatedness and evolutionary diversity among avihepadnavirus strains, a comprehensive analysis of the available 136 full-length viral genomes (n = 136) was conducted. The genomes were classified into two major genotypes, i.e., GI and GII. GI viruses were further classified into 8 sub-genotypes including DHBV-I (duck hepatitis B virus-I), DHBV-II (Snow goose Hepatitis B, SGHBV), DHBV-III, RGHBV (rossgoose hepatitis B virus), CHBV (crane hepatitis B virus), THBV (Tinamou hepatitis B virus), STHBV (stork hepatitis B virus), and HHBV (Heron hepatitis B virus). DHBV-I contains two sub-clades DHBV-Ia and DHBV-Ib. Parrot hepatitis B virus (PHBV) stains fall into GII which appeared as a separate phylogenetic branch/clade. All the subtypes of viruses in GI and GII seem to be genetically connected with viruses of DHBV-I by multiple mutational steps in phylogeographic analysis. Furthermore, 16 potential recombination events among different sub-genotypes in GI and one in GII were identified, but none of which is inter-genotypic between GI and GII. Overall, the results provide a whole picture of the genetic relatedness of avihepadnavirus strains, which may assist in the surveillance of virus spreading.