Two independent studies have demonstrated that viruses—and two strains of herpes in particular—are involved in Alzheimer’s disease. One study demonstrated that the herpes virus influenced the activity of many human genes—including
several that affect the risk of Alzheimer’s. The damage is particularly bad in the
brain samples of those who have the APOE4 gene. The second study found that amyloid could become over-activated by infections such as herpes and form plaques in an attempt to protect the brain. The research suggests that amyloid may
work alongside the immune system in responding to infections and other pathogens in the brain.