"Even oral Candida and herpes virus could possibly cause the inflammation in the brain that we see in Alzheimer's patients," said Olsen. Candida, a typically harmless fungus found in the mouths of half the world's human population, can become treacherous and lead to infection if it enters the bloodstream. And herpes simplex virus is present in more than 70 percent of the population after 50 years of age. It persists latently in the peripheral nervous system and is periodically reactivated in the brain.
Of Candida, Olsen and Singhrao wrote in the paper: "With a growing population of elderly, severe systemic fungal infections have increased dramatically in this age group during the last 30 years. Oral yeasts can be found in periodontal pockets, in root canals, on the mucosae and underneath dentures (denture stomatitis) (140-142). … Fungal molecules including proteins and polysaccharides [(1,3)-β-glucan] were detected in peripheral blood serum, and fungal proteins and DNA were demonstrated by PCR in brain tissue of AD patients."