The secret of how the cold sore virus manages to persist for a lifetime in the human body may have been cracked.
Herpes viruses manage to evade the immune system by shutting down.
This is why patients, once infected, have occasional flare-ups of cold sores or genital herpes, and can never get rid of the infection completely.
However, there is one thing that HSV-1 does produce, the precise role of which has puzzled scientists for some years.
It is a type of RNA, a single strand of genetic information copied from the DNA of the virus. In other viruses, these RNAs make proteins that are useful to the virus, but in herpes, this was not the case.
They found they were broken down into even smaller strands, called microRNAs, and these appeared to block the production of proteins which reactivated the virus.
Effectively, they were helping keep the virus in its dormant state.