The cold sore virus (HSV-1) currently infects an estimated 3.7 billion people worldwide. According to the World Health Organization (WHO), it is transmitted mainly by mouth-to-mouth contact and causes so-called "cold sores" or "cold sores", although it can also cause genital herpes.
Two-thirds of the world's population under the age of 50 are now carriers of the disease. For most, the occasional lip sore is embarrassing and/or uncomfortable, but in combination with other ailments (sepsis or even Covid-19, for example), the virus can be fatal. In 2018, two women died of herpes infection in the UK after cesarean delivery.
It turns out that the origin of this disease being a worldwide headache must be found around 5,000 years ago, when humans imported from the east a very common practice today, such as kissing. This is explained by the team from the University of Cambridge that has sequenced the ancient genome of the virus for the first time.
Their research, published in the journal Science Advances, suggests that the HSV-1 strain behind modern herpes arose from the great Bronze Age migrations to Europe from the steppe grasslands of Eurasia, and associated population booms. that boosted transmission rates.
The disease has a history stretching back millions of years, with different forms of the virus infecting species from bats to corals. Yet despite its contemporary occurrence among humans, scientists say finding ancient examples was surprisingly difficult.
Experts suggest that the Neolithic flourishing of facial herpes detected in the ancient DNA they have analyzed may have coincided with the advent of a new cultural practice: romantic and sexual kissing.
The researchers note that the earliest known record of kissing is a Bronze Age manuscript from South Asia, and suggest that the custom, far from being universal, may have traveled west with migrations to Europe from Eurasia.
In fact, centuries later, the Roman emperor Tiberius attempted to ban kissing at official functions to prevent the spread of disease, a decree that may have been related to herpes. However, for most of human prehistory, HSV-1 transmission would have been "vertical": the same strain passing from infected mother to newborn.
“The world has seen Covid-19 mutate at a rapid rate for weeks and months. A virus like herpes evolves on a much longer time scale,” explains Dr. Charlotte Houldcroft, co-author of the study. “Facial herpes hides in its host for life and is only transmitted by oral contact, so mutations occur slowly over centuries and millennia. We need to do deep research to understand how DNA viruses like this one evolve. Previously, genetic data for herpes only went back to 1925,” she added.
The researchers managed to find the virus in the remains of four individuals that were spread over a period of a thousand years and to extract the DNA they focused on the roots of the teeth, since herpes often breaks out with mouth infections. At least two of the bodies had gum disease and a third smoked tobacco.
The oldest sample came from an adult male unearthed in the Ural Mountains region of Russia, dating to the late Iron Age, about 1,500 years ago. Two further samples were from Cambridge: a woman from an old Anglo-Saxon burial ground a few miles south of the city dating to the 6th-7th centuries AD and an adult male from the late 14th century, entombed in the hospital grounds. city charity and had suffered from terrible abscessed teeth.
The latest sample came from a young man found in Holland who was an avid clay pipe smoker and was most likely massacred during a French attack on his village on the Rhine in 1672.
"We examined ancient DNA samples from around 3,000 archaeological finds and only got four herpes results," says Dr. Meriam Guellil. "By comparing the ancient genome with herpes samples from the 20th century, we were able to analyze the differences and estimate a mutation rate and, consequently, a timeline for the evolution of the virus," adds Dr. Lucy van Dorp.
But something happened about 5,000 years ago. "All primate species have a form of herpes, so we assume it has been with us since our own species left Africa. However, something happened millennia ago that allowed one strain of the virus to outcompete all others. Possibly was the increase in transmissions, which could be related to kissing," concludes Dr. Christiana Scheib.
