Alzheimer's disease could be caused by viruses like herpes, a group of dementia experts has warned. The worldwide team of 31 senior scientists and clinicians has written an editorial that suggests that microbes are the major cause of dementia.The herpes virus - the type that causes cold sores - and chlamydia bacteria are named as the major culprits, as well as a bacteria called spirochaete.Currently, most scientists are trying to find treatments that prevent the build-up of sticky amyloid plaques and misfolded tau proteins in the brain that prevent neurons from communicating with each other, leading to memory loss and cognitive decline.But in an the editorial in The Journal of Alzheimer's Disease, it is suggested that it is viral or bacterial infections that trigger the plaque build-up.Targeting them with antimicrobial drugs could halt dementia.Douglas Kell of the University of Manchester's School of Chemistry, said: "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.About two-thirds of people will acquire the herpes virus at some point in their lives, and many will not realise they have it.The herpes virus is known to damage the central nervous system, and the limbic system in the brain that regulates mood and instinct and is associated with mental decline and personality changes.They also point to the fact that a gene mutation - APOE e4 - which makes one in five people more susceptible to Alzheimer's disease, also raises their susceptibility to infectious disease.Last year researchers found that the "seeds" of Alzheimer's could be passed through blood transfusions and medical accidents. ..