APOE and Alzheimer disease: Lopatko Lindman et al. investigated a large nested case-control study and found an increased risk of developing AD in the association of APOE-ε4 heterozygotes and anti-HSV1 IgG carriage (OR 4.55, p = 0.02), compared with APOE-ε3 homozygotes, but none for carriage of either factor alone, nor for anti–HSV2 IgG, nor anti–CMV IgG.