Researchers believe that a specific strain of the herpes virus may cause some cases of unexplained infertility. Italian researchers examined the uteruses of 66 women with unexplained primary infertility and found that 43 per cent of them were infected by HHV-6A, one of the human herpes viruses. The virus was not found in any of the women whose fertility was normal.
Published in the journal PLoS One, the study describes how all the women infected with HHV-6A were found to have abnormal levels of cytokines, which are signaling proteins that facilitate interactions between cells that play an important role in supporting fertilized eggs and fetal development.
The virus is typically not detectable in the blood or saliva, so its true prevalence is unknown. However it replicates in the salivary glands and previous research indicates it can be transferred through kissing.