Scientists have reconstructed ancient genomes of human herpesviruses HHV-6A and HHV-6B from over 2,000-year-old European remains, proving these viruses have coexisted with humans for at least 2,500 years. The study reveals that some individuals inherited the viruses directly in their DNA, passed down through generations. One strain, HHV-6A, appears to have lost its ability to integrate into human chromosomes over time.
An international team of researchers, led by the University of Vienna and the University of Tartu in Estonia, has provided the first direct genetic evidence of a long-standing relationship between humans and human betaherpesviruses 6A and 6B (HHV-6A/B). Published in Science Advances, the findings stem from analyzing nearly 4,000 skeletal samples from archaeological sites across Europe. From this effort, the team successfully rebuilt eleven ancient herpesvirus genomes, dating back more than 2,000 years.
The oldest sample comes from a young girl in Iron Age Italy, between 1100 and 600 BCE. Other remains span medieval periods in England, Belgium, and Estonia, as well as ancient Italy and early historic Russia. Notably, several individuals from England carried inherited forms of HHV-6B, marking the earliest known cases of chromosomally integrated human herpesviruses. The site of Sint-Truiden in Belgium yielded the most cases, showing both viral strains circulated in the same community.
HHV-6B, which infects about 90 percent of children by age two and causes roseola infantum—the leading trigger for febrile seizures in toddlers—along with HHV-6A, belongs to a family of herpesviruses that establish lifelong dormancy after initial mild infections. Unlike most, these viruses can insert their genetic material into human chromosomes, allowing rare vertical transmission from parent to child. Today, roughly one percent of people carry such inherited copies.
"While HHV-6 infects almost 90% of the human population at some point in their life, only around 1% carry the virus, which was inherited from your parents, in all cells of their body," explained lead researcher Meriam Guellil from the University of Vienna's Department of Evolutionary Anthropology. "Based on our data, the viruses' evolution can now be traced over more than 2,500 years across Europe, using genomes from the 8th-6th century BCE until today."
Comparisons with modern data indicate some integrations happened thousands of years ago and persisted across generations. The study also highlights divergent paths: HHV-6A seems to have forfeited its integration capability early on, altering its host interactions as both evolved.
Links to contemporary health issues emerge too. "Carrying a copy of HHV6B in your genome has been linked to angina-heart-disease," noted Charlotte Houldcroft from the University of Cambridge's Department of Genetics. Inherited forms are more prevalent in the UK than elsewhere in Europe, and this research offers the first ancient evidence from Britain.
Overall, the work timestamps virus-human coevolution at the DNA level, illuminating how childhood infections can embed in our genetic legacy. Although identified in the 1980s, HHV-6's roots now extend to the Iron Age, supporting suspicions of coexistence since humans left Africa.