It almost seems improbable that the herpes virus would be linked to the development of Alzheimer’s disease. They are, after all, two entirely different diseases, with the former causing cold sores and the latter causing memory loss. But a new study finds that people carrying the herpes virus have double the risk of developing Alzheimer’s. Considering that almost everyone contracts one particular form of the virus, it could explain why so many people also develop Alzheimer’s.
Though herpes is normally believed to be a sexually transmitted disease, the virus actually comes in two forms, herpes simplex type 1 and type 2. It’s type 1 (HSV-1) that’s contracted by most people in childhood, and transmission doesn’t require a person to have symptoms, such as cold sores. According to the American Academy of Dermatologists, the virus is present in up to 90 percent of the population.
The correlation between the two diseases may be explained in a study from 2011. Researchers from three different institutions found that when these dormant viruses reactivated, they interacted with cellular membranes containing amyloid precursor proteins, the chemicals that cause the development of Alzheimer’s. During these interactions, they found that APP helped HSV-1 travel along the nerves. But at the same time, it was disrupting APP’s own transportation and distribution, a finding the researchers could spur production of amyloid plaques, a hallmark of Alzheimer’s disease.