The common cold sore virus, which is often caught in childhood, usually stays in the body for life – quietly dormant in the nerves. Now and then, things like stress, illness or injury can trigger it, bringing on a cold sore in some people. But this same virus – called herpes simplex virus type 1 – may also play an important role in something far more serious: Alzheimer’s disease.
Over 30 years ago, my colleagues and I made a surprising discovery. We found that this cold sore virus can be present in the brains of older people. It was the first clear sign that a virus could be quietly living in the brain, which was long thought to be completely germ-free – protected by the so-called “blood-brain barrier”.
