All in all, persistent HSV-1 infection and reactivation may present as risk factors, which likely interacts with and adds to other risk factors (e.g., age, ApoE4 genotype and other microbial infections) in the development of AD and other hippocampal-related brain disorders, as reviewed in Wainberg et al. (2021) and Vigasova et al. (2021). This evidence concerns the gene APOE and Alzheimer disease.