The worldwide team of 31 senior scientists and clinicians, which include specialists from Oxford, Cambridge, Edinburgh and Manchester Universities and Imperial College, have written an editorial which suggests that microbes are the major cause of dementia. Professor Douglas Kell of the University of Manchester’s School of Chemistry, said “We are saying there is incontrovertible evidence that Alzheimer’s Disease has a dormant microbial component. The authors say that viruses and bacteria are common in the brains of elderly people, and although they are usually dormant, they can ‘wake up’ after stress or if the immune system is compromised. (ii) Herpes simplex encephalitis (HSE) produces damage in localized regions of the CNS related to the limbic system, which are associated with memory, cognitive and affective processes [15], as well as personality (the same as those affected in AD). Viral infections in the brain are already known to cause symptoms similar to Alzheimer’s and the experts say the link has been ‘neglected’ for too long. “Alzheimer’s disease causes great emotional and physical harm to sufferers and their carers as well as having enormously damaging economic consequences,” they write.  We are researchers and clinicians working on Alzheimer’s disease (AD) or related topics, and we write to express our concern that one particular aspect of the disease has been neglected, even though treatment based on it might slow or arrest AD progression. We refer to the many studies, mainly on humans, implicating specific microbes in the elderly brain, notably herpes simplex virus type 1 (HSV1), Chlamydia pneumoniae, and several types of spirochaete, in the etiology of AD [1–4]. “We propose that further research on the role of infectious agents in Alzheimer’s disease causation, including prospective trials of antimicrobial therapy, is now justified.” 
 
 They say new findings could also have implications for the future treatment of Parkinson’s Disease, and other progressive neurological conditions. There is some evidence to suggest that infections in general could ramp up the immune system and contribute to the progression of Alzheimer’s, but there isn’t conclusive evidence to suggest that a particular infectious agent or microbe could be directly responsible for causing the disease.
– 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.)