How the Cold Sore Virus Might Affect Alzheimer’s Disease

Experts warn that Alzheimer's disease may be linked to herpes simplex infections.


It's not uncommon for things to go together, like peanut butter and jelly. Surprisingly, there may now be a connection between cold sores and Alzheimer's disease.

In a recent editorial, 31 scientists from around the world noted that increasing evidence indicates viruses and bacteria may be the trigger for Alzheimer’s disease. The editorial took particular notice of herpes simplex (HSV1), which causes cold sores.

The scientists also pointed fingers at two bacteria: chlamydia and a spirochete. Chlamydia is a sexually transmitted infection. Spirochetes are coiled bacteria that can cause infections like Lyme disease.

Alzheimer's disease causes a gradual loss of memory and other cognitive functions. It results when plaques and protein malformations in the brain keep the cells from communicating properly. According to the scientists, a viral or bacterial infection triggers the damage that results in plaques.

“We are saying there is incontrovertible evidence that Alzheimer’s Disease has a dormant microbial component," Douglas Kell, PhD, and one of the editorial's authors, said in a press release. "We can’t keep ignoring all of the evidence.”

Dr. Kell is a researcher in bio-analytical science and professor at the University of Manchester’s School of Chemistry.

Dr. Kell and fellow authors cited research that indicates people with antibodies to HSV1 had twice the risk of developing Alzheimer’s disease compared to those who did not have antibodies. Antibodies indicate the HSV1 virus has been activated in the body.

Other studies indicated that HSV1 can increase the risk of Alzheimer’s disease in people who carry a gene mutation called APOEe4. The same gene mutation increases the susceptibility to infectious disease.

Previous research showed that viruses can cause neurological damage if they infect the brain.

Even if they have never had symptoms, about 60 to 90 percent of all adults carry HSV1 in their bodies. HSV1 can remain dormant in the body for many years. The virus can be triggered by stress or if the immune system is compromised.

The editorial has raised controversy in the scientific community.

“This is a minority view in Alzheimer's research," John Hardy, PhD, a geneticist and professor of neuroscience at University College of London, said in a press release. "There had been no convincing proof of infections causing Alzheimer's disease. We need always to keep an open mind but this editorial does not reflect what most researchers think about Alzheimer's disease.”

“There is growing evidence for the role of the immune system in Alzheimer’s and active ongoing research looking at how an inflammatory response might contribute to the disease," Simon Ridley, PhD and Director of Research at Alzheimer’s Research UK, said in a press release. "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.”

The editorial was published in the March Journal of Infectious Disease.