The rather unglamorous history of humans with cold sores hails from saucy origins, suggests a new study that found that the virus responsible for modern mouth sores probably flourished when romantic kissing became a common courting practice. The findings follow the first successful genome sequencing of ancient strands of herpes viruses that commonly cause lip sores.
We have HSV-1 to thank for the facial herpes that around 3.7 billion of us enjoy globally, which appears to have emerged as the dominant strain in the Bronze Age around 5,000 years ago, according to a new paper published in Science Advances. The authors believe a perfect storm of human migration, population density increases, and the advent of sexual-romantic kissing likely kicked off the dominant lineages that have endured into the modern era.
“The world has watched COVID-19 mutate at a rapid rate over weeks and months,” said co-senior author Dr Charlotte Houldcroft, from Cambridge’s Department of Genetics, in a statement.
“A virus like herpes evolves on a far grander timescale. Facial herpes hides in its host for life and only transmits through oral contact, so mutations occur slowly over centuries and millennia."
Previous genetic data on herpes only went back as far as 1925, so if Houldcroft and colleagues were to gain a better understanding of how DNA viruses like herpes evolve, they were going to need to go back a lot further.
Fortunately, they found their ancient cold sore specimens in four individuals whose lives spanned a period of over 1,000 years. From these, they were able to extract viral DNA from the roots of teeth containing herpes genomes, with the oldest dating back to the late Iron Age around 1,500 years ago.
In comparing the DNA of these ancient examples of cold sores with the modern strains, the team could establish a timeline for the virus’s evolution that revealed something interesting.
“Every primate species has a form of herpes, so we assume it has been with us since our own species left Africa,” said co-senior author Dr Christiana Scheib, 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.”
Kissing first emerges in human records in a manuscript from the Bronze Age which indicated the practice of mashing together your mouth parts as a means of expressing affection may have spread westward from South Asia into Europe and Eurasia.
While pandemics like COVID-19 mean that modern humans are acutely aware of the potential pathogen spread from such interactions, the role of kissing in disease has been long understood. Roman Emperor Tiberius was certainly not into it having reportedly tried to ban kissing at events as a means of disease control, potentially in response to a strain of herpes.
Beyond curiosity, better understanding of viruses like herpes that affect so many and that have the potential to be fatal can contribute to our management of both HSV-1 and other diseases.
“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,” concluded Houldcroft.
The researchers intend to continue their work further back into human history, as Scheib put it: “Neanderthal herpes is my next mountain to climb.”