When did humans become infected with the herpes simplex virus which causes cold sores? With 20 to 30% of the UK population suffering from recurring outbreaks, and an estimated 67% of the global population carrying the oral (HSV-1) or genital (HSV-2) variation of the virus, it is certainly a mystery that needed solving.
A team of scientists from San Diego AntiViral Research Center in California think they have discovered how and when human beings first started suffering from cold sores.
The answer lies with our hominid ancestors and the ancestors of modern monkeys. The researchers applied "a Branch-Site Random Effects Likelihood model of molecular evolution" to their study, which allowed "the strength of natural selection to vary across both the viral phylogeny and the gene alignment".
Using this model, they found that it was most likely that at least 1.6 million years before modern human beings evolved from chimps and we each became our own distinct species, we became infected with HSV-1. This virus then co-diverged with us as we slowly evolved to become modern humans.
The scientists state that HSV-2 was probably the result of, "a cross-species transmission event from the ancestor of modern chimpanzees to an extinct Homo precursor of modern humans".
This wouldn't be the first time that a virus was transferred from one species to another. For instance, according to the World Health Organization, Ebola was passed to humans by infected fruit bats and other animals in 1976. Furthermore, The Aids Institute states that HIV and AIDs was passed to humans by chimpanzees, potentially around the 1940s, when hunters in West Africa ate chimpanzee meat and became infected by the simian immunodeficiency virus.
Despite the cold sore virus having been around for millennia, there is unfortunately no cure for it as yet. However, there are treatments such as Herstat available for the unpleasant symptoms.
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Photo © Terry Robinson via Flickr, under Creative Commons Licence
