MAPT and Alzheimer disease: This review deals not only with updates on topics that were covered in the author’s most recent review, but also with topics not covered previously, namely, the possibility that cytomegalovirus (CMV) rather than HSV1 is a cause of AD; epidemiological studies on HSV/HSV1-specific humoral responses; genetic studies; evidence of reactivation of HSV1 in the CNS; effects of infection of mouse brains on Aβ and P-tau; studies on HSV1-infected cell cultures; and the case for antiviral treatment for AD patients.