A new research suggests that humans have been fighting Herpes Simplex Virus (HSV) for around six million years.

Herpes Simplex Virus infected early hominids even before their evolutionary split from chimpanzees, a new study by the University of California, San Diego School of Medicine found.

Researchers were looking at the origins of the virus strains that cause herpes and humans. They found that the human herpes simplex virus (HSV) -1 infected hominids some 6 million years ago whereas the HSV 2 virus jumped to humans around 1.6 million years ago.

Herpes Simplex Virus is common in the U.S as well as elsewhere and it causes sores and blisters around mouth or genital areas.

"Humans are the only primates we know of that have two herpes simplex viruses," said Joel O. Wertheim, PhD., assistant research scientist at the UC San Diego AntiViral Research Center and lead author of the study. "We wanted to determine why."

For the study, researchers looked at the genetic sequence of HSV-1 and HSV-2 and compared it with genetic data on the family of simplex viruses from eight monkey and ape host species. Researchers used advanced models of molecular evolution to see when the viruses diverged from each other.

"The results help us to better understand how these viruses evolved and found their way into humans," Wertheim said in a news release "Animal disease reservoirs are extremely important for global public health. Understanding where our viruses come from will help guide us in preventing future viruses from making the jump into humans."

Researchers found that HSV 2 was more genetically similar to the herpes virus found in chimpanzees. The team estimated that humans might have acquired the Herpes virus from an ancient ancestor of chimpanzees some 1.6 million years ago.

The study is published in the Molecular Biology and Evolution and is funded by University of California Laboratory Fees Research Program.