Itzhakiet al. found that AD patients with the HSV-1 DNA have ahigher presence of the APOE4 allele than in a HSV-1 negative AD group,HSV-1 negative non-AD group, and HSV-1 positive non-AD group (52.8%,10%, 6.3%, and 3.6%, respectively) with respect to allelic frequencyof APOE4 in each group.20 This evidence concerns the gene APOE and Alzheimer disease.