Researchers in Italy have found evidence to suggest that an obscure virus spread through saliva - i.e. kissing - might actually be linked to unexplained infertility in women.

As well as giving you second thoughts the next time you lock lips with someone, the discovery could also offer hope and a new treatment option to some of the 10 percent of women who have problems conceiving children.

It's not the first time the virus, known as HHV-6A (one of several human herpes viruses) has been linked to kissing, but no one has made the association with infertility before, reports Henry Bodkin for The Telegraph.

The team - led by Roberta Rizzo from Univeristy of Ferrara in Italy - tested 30 women with unexplained fertility problems and found that 13 (43 percent) had an HHV-6A infection in their uterus. The human herpes virus was not detected in another 36 healthy women tested as a control group.

HHV-6A is still largely a mystery to scientists, and the majority of infections of both HHV-6A and its close relation HHV-6B are 'silent', meaning they usually don't express any noticeable symptoms.

In this study, all the women carrying HHV-6A were also found to have abnormally high levels of cytokines - signalling proteins that help cells interact, and play an important role in the development of a fertilised egg and foetus.

High levels of the hormone estradiol were also found, and the researchers think that the hormone might be triggering the HHV-6A infection in some way.

While the results are certainly off-putting, there's somewhat of a silver lining here, because if scientists can figure out how to treat the infection, it would mean affected women are able to conceive without resorting to the expensive and complicated process of in vitro fertilisation (IVF).

Right now, though, there are no approved treatments for either HHV-6A or HHV-6B.

"This is a surprising discovery," HHV-6 specialist Anthony Komaroff from Harvard Medical School, who wasn't involved in the study, told The Telegraph. "If confirmed, the finding has the potential to improve the outcome for a large subset of infertile women." 

While we know relatively little about HHV-6A, previous studies have shown it can be passed on by saliva, which is why kissing has been linked to the report.

But it's likely that a range of other biological factors are at play to trigger an HHV-6A infection - even if a kiss can transmit it - factors that will now have to be investigated as scientists try to work out exactly what's going on.

"Further studies are required to confirm the association of HHV-6A infection as a trigger of female primary unexplained infertility," conclude the researchers in their report. "Indeed, there are several potential mechanisms by which HHV-6 might induce female infertility."

In the meantime, there's no need to stop kissing - as long as you know the facts about what you might be passing on.

The team's findings were published in the journal PLOS One.