title: Enigmatic origin of hepatitis B virus: an ancient travelling companion or a recent encounter?
abstract: Hepatitis B virus (HBV) is the leading cause of liver disease and infects an estimated 240 million people worldwide. It is characterised by a high degree of genetic heterogeneity because of the use of a reverse transcriptase during viral replication. The ten genotypes (A-J) that have been described so far further segregate into a number of subgenotypes which have distinct ethno-geographic distribution. Genotypes A and D are ubiquitous and the most prevalent genotypes in Europe (mainly represented by subgenotypes D1-3 and A2); genotypes B and C are restricted to eastern Asia and Oceania; genotype E to central and western Africa; and genotypes H and F (classified into 4 subgenotypes) to Latin America and Alaska. This review summarises the data obtained by studying the global phylodynamics and phylogeography of HBV genotypes, particularly those concerning the origin and dispersion histories of genotypes A, D, E and F and their subgenotypes. The lack of any consensus concerning the HBV substitution rate and the conflicting data obtained using different calibration approaches make the time of origin and divergence of the various genotypes and subgenotypes largely uncertain. It is hypothesised that HBV evolutionary rates are time dependent, and that the changes depend on the main transmission routes of the genotypes and the dynamics of the infected populations.
authors: Gianguglielmo Zehender, Erika Ebranati, Elena Gabanelli, Chiara Sorrentino, Massimo Galli, L. Sacco Department of Biomedical and Clinical Sciences, University of Milan, 20157 Milan, Italy.
authors: Gianguglielmo
authors: G
authors: Zehender
authors: Gianguglielmo Zehender, Erika Ebranati, Elena Gabanelli, Chiara Sorrentino, Massimo Galli, L. Sacco Department of Biomedical and Clinical Sciences, University of Milan, 20157 Milan, Italy.
authors: Erika
authors: E
authors: Ebranati
authors: Gianguglielmo Zehender, Erika Ebranati, Elena Gabanelli, Chiara Sorrentino, Massimo Galli, L. Sacco Department of Biomedical and Clinical Sciences, University of Milan, 20157 Milan, Italy.
authors: Elena
authors: E
authors: Gabanelli
authors: Gianguglielmo Zehender, Erika Ebranati, Elena Gabanelli, Chiara Sorrentino, Massimo Galli, L. Sacco Department of Biomedical and Clinical Sciences, University of Milan, 20157 Milan, Italy.
authors: Chiara
authors: C
authors: Sorrentino
authors: Gianguglielmo Zehender, Erika Ebranati, Elena Gabanelli, Chiara Sorrentino, Massimo Galli, L. Sacco Department of Biomedical and Clinical Sciences, University of Milan, 20157 Milan, Italy.
authors: Alessandra
authors: A
authors: Lo Presti
authors: Gianguglielmo Zehender, Erika Ebranati, Elena Gabanelli, Chiara Sorrentino, Massimo Galli, L. Sacco Department of Biomedical and Clinical Sciences, University of Milan, 20157 Milan, Italy.
authors: Elisabetta
authors: E
authors: Tanzi
authors: Gianguglielmo Zehender, Erika Ebranati, Elena Gabanelli, Chiara Sorrentino, Massimo Galli, L. Sacco Department of Biomedical and Clinical Sciences, University of Milan, 20157 Milan, Italy.
authors: Massimo
authors: M
authors: Ciccozzi
authors: Gianguglielmo Zehender, Erika Ebranati, Elena Gabanelli, Chiara Sorrentino, Massimo Galli, L. Sacco Department of Biomedical and Clinical Sciences, University of Milan, 20157 Milan, Italy.
authors: Massimo
authors: M
authors: Galli
mesh_terms: D019143:Evolution, Molecular; D005838:Genotype; D006509:Hepatitis B / Q000453:epidemiology / Q000635:transmission / Q000821:virology*; D006515:Hepatitis B virus / Q000235:genetics* / Q000472:pathogenicity; D006801:Humans; D017720:Molecular Epidemiology; D010641:Phenotype; D010802:Phylogeny; D058974:Phylogeography; D011157:Population Dynamics
keywords: Hepatitis B virus genotypes and subgenotypes; Hepatitis B virus phylodynamics; Molecular epidemiology; Phylogeography; Population dynamics and epidemics