As you may know, loss of the sense of smell is one of the, if not the earliest sign of neurodegenerative disease. So for example, in Parkinson's disease, there's loss in the sense of smell probably 10 years before any other symptom. People have failed to make this a diagnostic tool because it's nonspecific.

So it's not as if you could come to your doctor and say, "I'm losing my sense of smell," and they'll say, "Oh, early sign of Parkinson's," because you can have many reasons to lose your sense of smell and so on. Olfactory loss, again, is an early sign of neurodegeneration.

And there's at least one theory, particularly about Alzheimer's disease, suggesting that Alzheimer's may be the result of a pathogen that enters the brain through the olfactory system. Interesting. It's not, of course, a mainstream or widely accepted theory of any type, but it just highlights this notion that the nose is a path to our brain.