[giantg2]

HSV1 is estimated to affect more than 80% of the population, but less than 80% have dementia. This seems to imply there are other factors at play. Maybe it requires other factors like genetics or immune issues for it to progress.

[amanaplanacanal]

I can't point to a citation but I'm sure I've seen it hypothesized that it requires both the infection, then some sort of injury to allow the virus to cross the blood brain barrier.

[giantg2]

Or maybe they come through with the microplastics.