Lip herpes may have coincided with the emergence of a new cultural practice imported from the east 5,000 years ago: romantic kissing.
The ancient genomes of the herpes virus, which commonly causes lip sores and currently infects around 3.7 billion people worldwide, have been uncovered and sequenced.
Recent research shows that the HSV-1 virus behind facial herpes as we know it today emerged around 5,000 years ago, following massive Bronze Age migrations from the steppe grasslands of Eurasia to Europe and associated population explosions that increased transmission rates.
Herpes has a history stretching back millions of years and forms of the virus infect many species, from bats to corals. However, despite its contemporary prevalence among humans, scientists say it is surprisingly difficult to find ancient samples of HSV-1.
The authors of the study, published in the journal Science Advances, say the Neolithic development of facial herpes detected in ancient DNA may have coincided with the emergence of a new cultural practice imported from the east: romantic and sexual kissing.
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“The world has watched COVID-19 mutate at a rapid rate over weeks and months,” said Dr. Charlotte Houldcroft, senior author of the study from the Cambridge Department of Genetics. A virus like herpes evolves on a much larger timescale.”
“Facial herpes hides in the host for their lifetime and is transmitted only through oral contact, so mutations occur slowly over centuries and millennia. We need to conduct long-term research to understand how DNA viruses like this evolve. Previously, genetic data for herpes only dated back to 1925.”
The team was able to extract viral DNA from cold sores and tooth roots from the remains of four individuals spanning a thousand-year period. Herpes is often exacerbated by oral infections: at least two of the ancient cadavers had gum disease and the third smoked tobacco.
The oldest specimen came from an adult male excavated in the Ural Mountain region of Russia and dated to the late Iron Age, around 1,500 years ago.
Two specimens were from England. One was a woman from the 6th-7th centuries AD from an early Anglo-Saxon cemetery a few kilometers south of the city. The other was a young adult male from the late 14th century, suffering from terrible dental abscesses, buried in the grounds of a hospital in medieval Cambridge.
The final specimen came from a young adult male excavated in the Netherlands: a passionate clay pipe smoker, most likely slaughtered in a French attack on his village on the Rhine in 1672.
“We screened ancient DNA samples from nearly 3,000 archaeological finds and got only four herpes hits,” says co-author Dr. Meriam Guellil from the Institute of Genomics at the University of Tartu.
“By comparing the ancient DNA with herpes samples from the 20th century, we were able to analyze the differences and estimate a mutation rate and therefore a timeline for virus evolution,” says study co-author Dr. Lucy van Dorp of the UCL Institute of Genetics.
Co-senior author Dr. Christiana Scheib said, “Every primate species has a form of herpes, so we assume it has been with us since our own species left Africa. However, about five thousand years ago, something happened that allowed one form of herpes to overtake others, possibly an increase in transmissions, which could be linked to kissing.”
The researchers point out that the earliest known record of kissing is a Bronze Age manuscript from South Asia, and suggest that the custom, which is far from universal across human cultures, may have traveled westward with migrations from Eurasia to Europe.
In fact, centuries later, the Roman Emperor Tiberius tried to ban kissing at official ceremonies to prevent the spread of the disease, a decree that may have been related to herpes. For most of human prehistory, however, HSV-1 transmission had to be “vertical”: that is, the strain passed from infected mother to newborn child.
According to the World Health Organization, two-thirds of the global population under the age of 50 currently carries HSV-1. For most of us, occasional lip sores are embarrassing and uncomfortable, but in combination with other ailments (e.g. sepsis and even COVID-19) the virus can be deadly. In 2018, two women died from HSV-1 infection following caesarean sections in the UK.
“Genetic samples that are only 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, react to each other,” says Houldcroft.
The team wants to track this hardy primitive disease even deeper in time to investigate infection of early hominins. “Neanderthal herpes is my next research focus,” says Scheib.
University of Cambridge. July 27, 2022:
Guellil, M., van Dorp, L., Inksip, S. A., Dittmar, J. M., Saag, L., Tambets, K., … & Scheib, C. L. (2022). Ancient herpes simplex 1 genomes reveal recent viral structure in Eurasia. bioRxiv.