Viral DNA samples from 4 ancient cadavers suggest that HSV-1 transmission boomed with Bronze Age migrations and the introduction of kissing as a romantic and sexual cultural practice.
The herpes simplex virus I (HSV-1) strain behind facial herpes arose 5000 years ago during the Bronze Age, possibly driven by the introduction of kissing as a cultural practice through migration, according to research published in Science Advances.
For the first time, an international team of scientists led by the University of Cambridge have uncovered and sequenced ancient genomes from the herpes virus that commonly causes lip sores. Researchers suggest that the population booms at the time of the Bronze Age migrations into Europe from the Steppe grasslands of Eurasia drove rates of transmission.
Herpes is known to have existed for millions of years with forms of the virus infecting species from bats to coral. However, scientists say that it was surprisingly hard to find ancient examples of HSV-1 in humans, despite the contemporary prevalence of the disease among humans.
“Facial herpes hides in its host for life and only transmits through oral contact, so mutations occur slowly over centuries and millennia. We need to do deep time investigations to understand how DNA viruses like this evolve,” said Dr Charlotte Houldcroft, MA, PhD, from Cambridge’s Department of Genetics, in a statement. “Previously, genetic data for herpes only went back to 1925.”
The team found herpes in the remains of 4 individuals stretching over a 1000-year period. They extracted viral DNA from the roots of the teeth, given that herpes often flares up with mouth infection. At least 2 of the ancient cadavers had gum disease and a third smoked tobacco.
“We screened ancient DNA samples from around 3000 archaeological finds and got just four herpes hits,” said Meriam Guellil, BA, MSc, PhD, from Tartu University’s Institute of Genomics.
The oldest sample was sourced from an adult male that was excavated in Russia’s Ural Mountain Region. This sample dated from the late Iron Age around 1500 years ago.
An additional 2 samples were local to Cambridge. The first was a female from an early Anglo-Saxon cemetery a few miles south of the city, dating from 6-7th centuries CE.
The other sample came from a young adult male from the late 14th century who had suffered dental abscesses. He had been buried in the grounds of medieval Cambridge’s charitable hospital, which later became St. John’s College.
The fourth sample came from a young adult male and avid clay pipe smoker who had been excavated in Holland. Researchers suggest that he may have been massacred by a French attack on his village by the banks of the Rhine in 1672.
“By comparing ancient DNA with herpes samples from the 20th century, we were able to analyse the differences and estimate a mutation rate, and consequently a timeline for virus evolution,” said Lucy van Dorp, MSc, MRes, PhD, from the UCL Genetics Institute.
The authors say that the Neolithic flourishing of facial herpes detected in the ancient DNA may have coincided with the advent of romantic and sexual kissing as a new cultural practice. They suggest the custom, which was far from universal in human cultures, may have travelled westward with migrations into Europe from Eurasia.
“Every primate species has a form of herpes, so we assume it has been with us since our own species left Africa,” said Christiana Scheib, MA, MPhil, PhD, research fellow at St. John’s College, University of Cambridge, and head of the Ancient DNA lab at Tartu University. “However, something happened around five thousand years ago that allowed one strain of herpes to overtake all others, possibly an increase in transmissions, which could have been linked to kissing.”
However, for most of human prehistory, HSV-1 transmission would have been vertical, meaning that the same strain was passed from infected mother to newborn child. Currently, two-thirds of the global population under the age of 50 now carry HSV-1, according to the World Health Organization.
Though many people experience occasional lip sores resulting only in mild embarrassment and discomfort, in combination with other ailments such as sepsis or COVID-19, the HSV-1 virus can be fatal.
“The world has watched COVID-19 mutate at a rapid rate over weeks and months. A virus like herpes evolves on a far grander timescale,” Houldcroft noted.
She added, “Only genetic samples that are hundreds or even thousands of years old will allow us to understand how DNA viruses such as herpes and monkeypox, as well as our own immune systems, are adapting in response to each other.”
The researchers would like to trace the disease even further back in time, investigating infection of early hominins.
“Neanderthal herpes is my next mountain to climb,” Scheib said.
Prehistoric roots of ‘cold sore’ virus traced through ancient herpes DNA. EurekAlert; News Release. July 27, 2022. Accessed August 1, 2022. https://www.eurekalert.org/news-releases/959525