According to World Health Organization (WHO)  there are an estimated 257 million people suffering from hepatitis B virus infection which attacks liver and result into hepatocellular carcinoma. The virus is transmitted via contact i.e.  blood transfusion, mother to fetus, daily used items where carving of human skin is involved and razor blade or injection use which is already applied to an infected person. Every year approximately one million deaths occur due to this disease. Hepatitis B virus is a partially double stranded DNA virus. It is a species of the genus Orthohepadnavirus, and a member of the Hepadnaviridae family of viruses.
However this disease is not a new in human medical history because its presence in human remains of approximately 4 thousand years old has been confirmed. In a study which was conducted recently in Cambridge university, the researchers have found that ancient humans had hepatitis B virus in their genomes. This shows that this disease had been a part of human illness approximately four thousand years ago. This era in history has been called as late Bronze Age and Iron Age of human civilization.
According the study researchers they analysed data which was sequenced with Shotgun sequencing, a technique more effective than targeted PCR  technique. “We identified reads that matched the HBV genome in spanning a period of almost 4,000 years, from several different cultures and with a broad geographical range”.
The data of 12 selected samples was phylogenetic analysed with the ancient HBV genomes, which were confirmed as the old world HBV genome and recombination also occurred to form an old HBV and an unknown genome, similarly other recombinations also found with modern genotype A,old and modern genotype B and two other modern genotype C.  The genotype A of old HBV genomes was found in Sintashta culture and Scythian culture which belonged to Russia and Hungry respectively. Hungrian culture Scythians were in the age of Bronze era. This genotype A has two subgenotype A1 and A3 which were carried into Africa. Genotype D sequences were all belogned to Central Asia in Kazakhstan and their modern version was proved to be found among Paharia people in India.
The data also proves that today’s diversity is a subset of the diversity present in ancient age genome. The present genotype do not reveal complexity in genotype as compared to ancient genotype where genotype A was created via recombination and outside Africa its emergence occurred. In the modern genotype substitution rate obtained which is not according to the ancient form. This research was published in Nature.

References:

B. Mühlemann et al., “Ancient hepatitis B viruses from the Bronze Age to the Medieval period,” Naturedoi:10.1038/s41586-018-0097-z, 2018

Allentoft, M. E. et al. Population genomics of Bronze Age Eurasia. Nature 522, 167–172 (2015).