Analyzes of more than 300 ancient human genomes have shown that Hepatitis B virus in humans is at least 4,500 years old and is much older than modern viral genomes.
Hepatitis B virus (HBV), which damages the liver, kills one million people every year. Now new genetic studies show that this pathogen has been with us at least since the dawn of civilization.
Until now, the earliest evidence for hepatitis B virus was discovered in an Italian mummy of the 16th century. In a new study, a team led by a geneticist, Eske Willerslev, sequenced the genomes of 304 people in archaeological sites in Eurasia, dating back to the Iron Age (about 3500 BC to about 500 BC), the majority of which were in the Bronze Age. The team quickly identified the genetic residue of HBV in 12 individuals. The earliest example of these individuals was about 4500 years old and was found in an old grave in Osterhofen, Germany.
The team then compared the DNA sequences of these old viruses with modern HBV versions and used advanced mathematical modeling techniques to predict how long these variations would occur, given the prevalence of populations over time. The data showed that the virus most likely occurred between 13.600 and 9.600 BC
In another study conducted under the leadership of the Geneticist Johannes Krause from the Max Planck Institute for the Study of Human History, three skeletons in Germany, dating from 5,000 to 3,200 BC, were found in the tooth core of HBV
"When the results of both studies are taken into consideration, HBV looks pretty common in the past," says Krause. Krause says this should not be a surprise, but future researchers have shown a way to investigate other ancient diseases.
A popular hypothesis that chimpanzees and gorillas have very similar HBV strains to humans suggests that the virus may have originated in Africa, then hunting or splashing people through blood contact while cutting their flesh. Then, the virus may have multiplied in different species with people who have been draining Eurasia 120,000 to 80,000 years ago.
The findings of Willerslev's team suggest an interesting alternative: Although this sort of transmission mechanism seems mixed, HBV may have emerged more recently in Eurasia and even in North America, then Africa may be transferred to both humans and nonhuman primates.
This timetable also coincides with the beginning of human civilization, which will help larger populations and trade routes to spread to the disease and turn into new species.
Krause, however, doubts as to when the virus came into being. "HBV reassembles the carrier's genetic material, so typical molecular dating techniques based on genetic mutation rates do not work."
The evolutionary geneticist Hendrik Poinar, who is not involved in the research, acknowledges that these limitations make it difficult to speculate about the chronological origins of the virus based on current data. "At this point it would be risky to say something about the history of the origins of HBV."
Regardless of the origin of HBV, however, "These investigations really show that you can find examples of pathogens that have been in DNA for thousands of years. The interaction of this virus with people is a dynamic that has been around for thousands of years. "
Sciencemag. May 9, 2018.
Article : Krause-Kyora, B., Susat, J., Key, FM, Kuehnert, D., Bosse, E., Immel, A., … & Hey, HO (2018). Neolithic and Medieval virus genomes reveal complex evolution of Hepatitis B. bioRxiv, 315531.