The line between the human herpes simplex viruses – HSV-1 and HSV-2 – is blurrier than previously thought, according to a new study published this week  in The Journal of Infectious Diseases.

Herpes simplex virus in a laboratory culture.
Image/Greg Pepper

Researchers found that HSV-1 and HSV-2 are mixing together to result in several new, different recombinant versions of herpes.

Read the paper

“The main implication is that HSV-1 and HSV-2 are continuing to recombine,” said lead author Dr. Amanda Casto, a senior fellow in infectious diseases at the University of Washington School of Medicine. “This could have important implications for HSV vaccine development, because it means a live HSV-2 vaccine could recombine with circulating HSV-1 strains, thereby forming an infectious virus.”

HSV-1 and HSV-2 are two of the most common viruses affecting people. Moreover, humans are the only mammals that have two types of herpes simplex viruses.

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Both viruses look alike clinically and are sensitive to the same drug, acyclovir. But they are genetically different.  HSV-1 most commonly affects the mouth, while HSV-2 usually causes genital lesions.

More than two-thirds of the world’s population is estimated to be infected with one or both viruses, according to the World Health Organization.

Read more at UW Medicine