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.

Hepatitis B virus genotypes: epidemiological and clinical relevance in Asia

“…Genotype J has been described in Japan and Ryukyu [3]. Numerous subgenotypes have been described in Asia, including A1, B1-B5 and B7-B9, C1-C2 and C5-C16, D1-D6 and D9, and I1-I2 [4]. These sub-genotypes appear to be geographically constrained and evolve independently of each other.…”

“…Genotypes A and D are ubiquitous but most prevalent in Europe and Africa; genotypes B and C are confined to Asia and Oceania [3,4]. Infections with other genotypes such as E, F, G and H are also occasionally observed in Asia.…”

“…It has been hypothesized that evolutionary rates are time dependent, and the changes depend on the dynamics of the infected populations and the main transmission routes of the genotypes. The phylogeographic framework would shed light on the geographic origin and global spread of HBV genotypes and sub-genotypes throughout different populations [4].…”

Diagnosis of hepatitis B

“…According to the sequence divergence, HBV can be divided into ten genotypes, labelled A-J: they have distinct geographic distribution (24). Genotype B and C are restricted to Oceania and Asia, whereas genotype A and D are omnipresent but most common in Africa and Europe (25). Genotype I is unusual and can be observed in Vietnam, Laos, India and China, while genotype J has been reported in Japan and Ryukyu (26,27).…”

Comparison of Detection Rate and Mutational Pattern of Drug-Resistant Mutations Between a Large Cohort of Genotype B and Genotype C Hepatitis B Virus-Infected Patients in North China

“…1,2 So far, nine genotypes named by alphabetical capital letters (A-I) have been defined by a sequence divergence of more than 8% in the entire genome, which have distinct ethnogeographical distribution. 3,4 In China, HBV/C and HBV/B were two major ones, distributing predominantly in North and South China, respectively. 5,6 Nucleos(t)ide analogues (NAs) are commonly used in clinic.…”