MAPT and Alzheimer disease: As discussed briefly throughout this review, there are several recognized potential mechanisms proposed for the virus–AD hypothesis which encompass direct neuronal infection, chronic neuroinflammation, altered Aβ processing, tau protein dysregulation, immune system dysregulation, blood–brain barrier disruption, and genetic and epigenetic interactions that may contribute to the development or exacerbation of AD, as shown in Figure 2, which we will briefly elaborate on next.