The virus that causes cold sores may also lead to something far worse: Alzheimer's disease.
A new study - published Monday in the Journal of Pathology - links the herpes simplex virus to the devastating disease that affects 20 million people worldwide.
Researchers at the University of Manchester found that 90% of the protein plaques in Alzheimer's sufferers' brains contain the virus. Protein plaques are a key abnormality in the brains of those afflicted.
Ruth Itzhaki, who has been investigating the disease for 18 years, said her team believes the herpes simplex virus 1 is a "major" cause of the disease. But she cautioned that "there's no evidence that people who get cold sores are going to get Alzheimer's." It's also necessary to have a specific genetic variant that makes people vulnerable, she said.
Itzhaki said the research suggests that anti-viral medicine such as acyclovir - currently used to treat cold sores - could be an effective treatment for Alzheimer's.
"It would stop what we think is a major cause, rather than stopping symptoms only" as current treatments do, she said.
Most people carry the herpes simplex virus, which remains in the nervous system for their entire lives, and 20% to 40% of carriers get cold sores. The Manchester team believes the virus enters the brains of the elderly as their immune systems decline and establishes a silent infection which is activated by stress or other infections.
Alzheimer's organizations reacted cautiously to the study.
"This could lead to new treatments for Alzheimer's based on existing anti-viral agents," said Rebecca Wood of the Alzheimer's Research Trust.
But she added that "the underlying causes of Alzheimer's disease are still unknown."
