Roughly two-thirds of American adults have been exposed to the herpes type 1 virus (oral; type 2 is the genital one), and they could be predisposed to developing Alzheimer's disease later in life. So writes a group of 31 international scientists and clinicians in an editorial in the Journal of Alzheimer's Disease, stating that "substantial published evidence" suggests such a link and calling on researchers elsewhere to take action. They claim that some microbes—the virus and two types of bacteria, chlamydia and spirochete—are linked to the progressive neurological disease. "We are saying there is incontrovertible evidence that Alzheimer's disease has a dormant microbial component," writes lead author Douglas Kell in a University of Manchester statement. "We can't keep ignoring all of the evidence."
The authors propose that the named microbes "reach the [central nervous system] and remain there in latent form." They can then essentially wake up during the course of aging, under stress, or as the immune system declines. "The consequent neuronal damage ... occurs recurrently, leading to ... ultimately AD," the authors posit. They point to the failure of 413 Alzheimer's drug trials conducted between 2002 and 2012 and "express our concern that one particular aspect of the disease has been neglected," as "antiviral/antimicrobial treatment of AD patients ... could rectify the 'no drug works' impasse." Meanwhile, not all are convinced, with one neuroscience professor framing theirs as a "minority view"; he tells the Telegraph there has "been no convincing proof of infections causing" the disease. (This 38-year-old's form of Alzheimer's is genetic.)