Conducted by researchers at the University of Manchester, the study suggests that the virus causing cold sores, known as herpes simplex virus 1 (HSV1), may be one of the main causes of Alzheimer's disease.
The research has implicated this virus in about 60 per cent of Alzheimer's cases.
Though their findings are preliminary, the researchers may transform scientific understanding of the brain disorder, and open an entirely new approach to treating it.
The new findings are significant in view of the fact that cheap antiviral drugs that can control HSV1 infections, such as acyclovir or Zovirax, have been available for many years, and are sufficiently safe to be sold over the counter.
The researchers say that treatments to prevent Alzheimer's from causing progressive damage may not take long to develop if HSV1's role is confirmed, and antivirals are proved effective against it in the brain.
"One thing that is exciting about our research is that we already have drugs that have been used for a relatively long time against HSV1, which are cheap and well tolerated. If we are right, there is a good chance we could make progress quite quickly," Times Online quoted Professor Ruth Itzhaki, who leads the research group, as saying.
The researchers revealed that the next step would be to test antivirals in early-stage Alzheimer's patients in a clinical trial, which would take three to five years.
An article describing the study has been published in the Journal of Pathology.