A virus that infects nearly all children early in life has, in rare cases, been present within human DNA for thousands of years. Recent research indicates that this relationship extends back to the Iron Age and that some people today still carry inherited copies of the virus in every cell of their bodies.
A recent study published in Science Advances describes how scientists reconstructed ancient genomes of Human betaherpesvirus 6 (HHV-6) from archaeological remains found across Europe. This research offers the first direct genetic evidence that HHV-6 has coevolved with humans for at least 2,500 years. These findings reveal a long-standing, close relationship between humans and a virus most people first encounter in early childhood.
A Common Virus With an Uncommon Ability
HHV-6 comes in two closely related forms, HHV-6A and HHV-6B. HHV-6B infects roughly 90 percent of children by age two. It causes roseola infantum, also called “sixth disease,” a leading cause of febrile seizures in young children. After the initial infection, the virus typically remains dormant in the body for life.
HHV-6 is unusual among common human viruses because it can integrate its genetic material into human chromosomes. Occasionally, the virus integrates into reproductive cells, enabling transmission from parent to child as part of the human genome. Today, about one percent of the population carries this genetically inherited virus.
Scientists suspected these inherited viral sequences originated in ancient times but lacked direct genetic evidence until now.
Mining Ancient DNA for Viral Genomes
To investigate this anomaly, an international team from the University of Vienna and the University of Tartu analyzed DNA from almost 4,000 human skeletal remains found at archaeological sites across Europe. The team was able to identify and reconstruct 11 ancient HHV-6 genomes from these samples.
Researchers found the oldest viral genome in the remains of a young girl who lived in Iron Age Italy between 1100 and 600 BCE. Other samples came from medieval sites in England, Belgium, Estonia, early historic Russia, and Italy. Both HHV-6A and HHV-6B were present in medieval remains, but only HHV-6B was found in the earlier samples.
“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,” said Meriam Guellil, lead researcher of the study at the University of Vienna’s Department of Evolutionary Anthropology. “These 1% of cases are what we are most likely to identify using ancient DNA, making the search for viral sequences quite difficult.”
Tracing Viral Evolution Across Millennia
The researchers traced the evolution of HHV-6 over more than 2,500 years by comparing ancient viral genomes with modern genetic data. Their analysis indicated that some viral integrations happened thousands of years ago and have persisted for generations.
The study also uncovered a key difference between the two types of the virus. HHV-6A appears to have lost its ability to integrate into human DNA early in its history, while HHV-6B has kept this unusual trait.
Modern Health Connections With Ancient Origins
These inherited HHV-6 sequences are more than genetic anomalies. Earlier research has linked chromosomally integrated HHV-6B to a higher risk of certain heart-related diseases.
“Carrying a copy of HHV6B in your genome has been linked to angina-heart-disease,” said Charlotte Houldcroft of the University of Cambridge’s Department of Genetics. “We know that these inherited forms of HHV6A and B are more common in the UK today compared to the rest of Europe, and this is the first evidence of ancient carriers from Britain.”
A New Perspective on Human and Virus Coevolution
Although HHV-6A and HHV-6B were first identified in the 1980s, modern genetic data had already suggested that these viruses may have evolved alongside humans since early migrations out of Africa. The discovery of ancient genomes now provides direct, time-stamped evidence of this long-standing relationship.
“This research traces their presence back to the Iron Age,” Guellil said. “These ancient genomes now provide first concrete proof of their presence in the deep human past.”
Beyond HHV-6, this study shows how ancient DNA can reveal the hidden history of infectious diseases. Infections that occur in childhood and seem to disappear can leave lasting traces, turning viruses into inherited parts of the human genome. Therefore, DNA can serve as a partial record of ancient epidemics that once moved quietly through entire populations.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds a Master of Business Administration, a Bachelor of Science in Business Administration, and a Data Analytics certification. His work combines analytical training with a focus on emerging science, aerospace, and astronomical research.