Unexplained infertility in women might be caused by a little-known herpes virus that can be transmitted with a kiss.
Researchers with the University of Ferrara in Italy say they've discovered a link between infertility and HHV-6A.
The team examined the uteruses of infertile women and discovered that 43% of them were infected by the virus, which can be transmitted through saliva.
The virus wasn't found in any of the fertile women they examined for the study published in the medical journal PLoS One.
The scientists who conducted the study, and others who work in the field, hope the finding will lead to better treatments.
"This is a surprising discovery," Anthony Komaroff, a professor at Harvard Medical School, told the Telegraph U.K. "If confirmed, the finding has the potential to improve the outcome for a large subset of infertile women."