Dementia, of which Alzheimer’s is the most common form, is one of the great health fears of our age. It already affects more than one in 100 Britons, and it is forecast to become more common as people live longer.

The Alzheimer’s Society estimates that dementia costs £17 billion every year. While drugs such as Aricept are available, they treat the disease’s symptoms not its cause, and work only for a while. They are also considered so expensive that their use is rationed by the NHS. A cheap drug that could stop the progression of Alzheimer’s would thus be a significant advance.

That is what the new research could promise. It is preliminary: all that has been established so far is that herpes simplex 1 infections are strongly associated with the disease. But the theory is biologically plausible, and the evidence intriguing.

Why, then, has the Manchester team struggled to obtain funding to continue its research? One reason may lie in its unorthodox approach. The notion that a germ as common as the cold sore virus might contribute to Alzheimer’s is an idea from left field, and scientists, especially those who hold the purse strings of funding bodies, are often deeply sceptical of such radical thinking.

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