In this review article, we aim to give an overview of the association between AD and the infectious agents SARS-CoV-2, HSV-1, CMV, EBV, Influenza viruses, T. gondii, HP, Spirochetes, CP, and P. gingivalis, focusing on the mechanisms by which these pathogens are related to the AD pathogenesis. This evidence concerns the gene CP and Alzheimer disease.