The modern strain of the virus that causes cold sores has been traced back to around 5,000 years ago, with researchers suggesting that the advent of kissing may have fueled its spread.
Around 3.7 billion people — the majority of the world’s population — have a lifelong infection with the HSV-1 virus behind facial herpes, according to the World Health Organization.
But despite its ubiquity, relatively little is known about the history of this virus or how it spread around the world.
That’s why an international team of researchers has screened the DNA of hundreds of people’s teeth from ancient archaeological finds.
They found four people who had the virus when they died, then sequenced their genomes for research published Wednesday in the journal Science Advances.
“Using these reconstructed genomes, we were able to determine that the variations of modern phyla all date back to some time in the late Neolithic and early Bronze Age,” said study co-author Christiana Scheib of the University of Cambridge.
“It was a bit surprising because it has long been thought that herpes is something that co-evolved with humans,” she told AFP.
– Unkissed –
She said that’s still true: All primate species have some form of herpes, and humans likely had an exposure when they first left Africa.
However, research showed that these earlier strains were replaced by the modern form around 5,000 years ago.
What caused this change? The researchers proposed two theories.
About 5,000 years ago was a time of great migration from Eurasia to Europe, and this spread may have affected the virus.
The other theory? That was around the time people started kissing romantically.
“This is definitely a way to alter the transmissibility of a herpes virus,” Scheib said.
The virus is usually passed from a parent to their child, but kissing would have given him a whole new way to jump between hosts, she said.
“There is some textual evidence for kissing between romantic partners in the Bronze Age,” said Scheib.
– ‘Far Greater’ –
The researchers said the earliest known record of kissing is a manuscript from South Asia during the Bronze Age, suggesting the custom may have migrated to Europe from Eurasia as well.
Kissing “is not a universal human trait,” Scheib pointed out, stressing that it’s difficult to pinpoint exactly when it began — or if it’s definitely linked to the spread of HSV-1.
Around 2,000 years ago, the Roman Emperor Tiberius is said to have tried to ban kissing on official occasions to prevent the spread of herpes.
Co-senior study author Charlotte Houldcroft, also from Cambridge, said a virus like herpes evolved on a “far greater timescale” than Covid-19, which the world has watched mutating in a matter of months.
“Facial herpes hides in its host for life and is only transmitted through oral contact, so mutations occur slowly over centuries and millennia,” she said.
“Previously, genetic data for herpes only went as far back as 1925,” she added, calling for further “deep time studies” of viruses.
“Only genetic samples hundreds or even thousands of years old will allow us to understand how DNA viruses like herpes and monkeypox, as well as our own immune systems, adapt in response to one another.”
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