Human herpesvirus 6 is nearly universal today, infecting most people in early childhood. New evidence suggests that this relationship is far older than modern medicine — and in some cases, far more permanent — than previously proven.
A new study published in Science Advances provides the first direct genetic evidence that this unusual relationship stretches back thousands of years. By reconstructing ancient genomes of human herpesvirus 6A and 6B (HHV-6A/B) from archaeological remains across Europe, researchers show that these viruses have been infecting — and in rare cases permanently integrating into — human chromosomes since at least the Iron Age.
The findings confirm that some herpesviruses didn’t just co-exist with early humans; they became part of the human genome itself.
"Modern genetic data suggested that HHV-6 may have been evolving with humans since our migration out of Africa," said lead researcher of the study, Meriam Guellil, in a press release. "These ancient genomes now provide first concrete proof of their presence in the deep human past."
From Childhood Infection to Inherited Virus
HHV-6B infects most children within the first two years of life and causes roseola infantum, a common childhood illness that is the leading cause of febrile seizures in young children. Along with its close relative HHV-6A, the virus typically remains dormant in the body after the initial infection.
What sets these viruses apart is their ability to insert their DNA into human chromosomes — a change that can be passed from parent to child and is found in about one percent of people today.
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Tracing Human Herpesvirus Across Millennia
For the recent study, the research team screened nearly 4,000 human skeletal remains from archaeological sites across Europe for traces of viral DNA. From that dataset, they could reconstruct eleven ancient genomes of human herpesvirus 6 — including the oldest, recovered from a young girl who lived in Italy during the Iron Age, between 1100 and 600 B.C.E. Additional genomes came from individuals in medieval England, Belgium, Estonia, Italy, and Russia.
"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. These 1% of cases are what we are most likely to identify using ancient DNA, making the search for viral sequences quite difficult," said Guellil.
Several of the English individuals carried inherited forms of HHV-6B, making them the earliest known people to harbor chromosomally integrated human herpesviruses. One site in Belgium, Sint-Truiden, stood out for yielding the largest number of cases, with both HHV-6A and HHV-6B present within the same population.
"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," added Guellil.
How a Virus Became Part of the Human Genome
By comparing ancient viral genomes with those circulating today, the researchers could pinpoint where HHV-6 inserted itself into human chromosomes and how long those insertions endured. Some integrations occurred thousands of years ago and persisted across many generations, offering dated snapshots of virus–human interactions frozen in time.
The analysis also revealed that the two closely related viruses did not evolve in tandem. HHV-6A appears to have lost its ability to integrate into human DNA relatively early, while HHV-6B retained it — evidence that even closely related viruses can diverge as they adapt to the same host.
Instead of relying on patterns in modern genomes alone, researchers now have direct genetic evidence showing when — and how — a common childhood virus crossed the boundary from infection to inheritance.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a recent study published in Science Advances: Tracing 2500 Years of Human Betaherpesvirus 6A and 6B Diversity Through Ancient DNA
