IT IS THE insidious and irritating virus which can causes cold sores on mouths and painful blisters on genitals.

And now, scientists say that there really was no escaping from the herpes virus: in fact, it infected humans before they had even become human.

Researchers in California found that one strand of herpes jumped from ancient chimpanzees to homo erectus, the ancestors of modern humans, around 1.6 million years ago.

The other strand infected hominids before they split from chimpanzees 6 million years ago, more than four million years before that.

“Understanding where our viruses come from will help guide us in preventing future viruses from making the jump into humans,” said Dr Joel O Wertheim, the lead author of the study and an assistant research scientist at the University of California.

It has been estimated that around two-thirds of the human population is infected with at least one herpes simplex virus, which usually appears as cold sores on the lips, or blisters on the genitals.

“Humans are the only primates we know of that have two herpes simplex viruses,” said Wertheim. “We wanted to determine why”.

The researchers compared the gene sequences of the herpes viruses to the family tree of other viruses from eight monkey and ape species, and were able to determine when and how the virusus evolved.

“Comparing virus gene sequences gave us insight into viral pathogens that have been infecting us since before we were humans,” said Wertheim.

The findings are published in the journal Molecular Biology and Evolution.

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