MAPT and Alzheimer disease: • Identified HHV-6 and HHV-7 in late-onset AD patients (Readhead et al., 2018) • Reduced autophagy, promoted accumulation of hyperphosphorylated Tau and Aβ peptides (Romeo et al., 2020) • Infected microglia enhanced Aβ peptide deposition and Tau phosphorylation (Bortolotti et al., 2019)