The article mentions that one of the viruses which seems correlated with Alzheimer's from multiple studies is HHV–6A and 99% of people carry that one, but for u

The article mentions that one of the viruses which seems correlated with Alzheimer's from multiple studies is HHV–6A and 99% of people carry that one, but for unknown reasons the viral infection is much more active in people with Alzheimer's symptoms, though the number of ApoE genes is correlated with risk of active viral infection/Alzheimer's per individual.