Experts say you could have this virus and not even know it. But the results of a new study suggest treating it may have unexpected benefits.
Research: Being Infected with This Surprising Virus Could Increase Your Alzheimer’s Risk
Published on Jun. 13, 2025
More than 7 million Americans are currently living with Alzheimer’s disease—and that number is expected to climb to nearly 13 million in the coming decades, according to 2025 data from the Alzheimer’s Association. Given that changes in the brain could begin “20 years or more before symptoms start,” per the organization, ongoing efforts to better understand potential risks remain crucial.
Interestingly, the results of a new study by a research team—representing the University of Washington’s Division of Allergy and Infectious Diseases and a biopharmaceutical company—indicate that there could be a link between a certain kind of infection and Alzheimer’s…and it’s an infection commonly experienced by at least half of the American adult population.
The researchers published details of their study in the medical journal BMJ Open, sharing that they set out to discover a potential “association between herpes simplex virus type 1 (HSV-1) and [Alzheimer’s disease] using real-world data.”
The highly contagious herpes simplex virus causes “oral herpes, genital herpes and infections in other areas of your body,” explains the Cleveland Clinic. While a large portion of people may not experience any symptoms, “fluid-filled blisters” can appear on the skin as signs of the virus.
Specifically, HSV-1, which an estimated 50 to 80% of U.S. adults have, typically causes oral herpes (also known as cold sores), according to Johns Hopkins Medicine. There’s no cure for the herpes virus, but treatment options such as topical ointments and oral medications are available.
Researchers used IQVIA PharMetrics Plus—an “expansive real-world dataset providing detailed insights into insured U.S. patients,” according to its website—to gather information about people aged 50 years or older who had been diagnosed with Alzheimer’s between 2006 and 2021. The team then matched each participant with a control subject who also had Alzheimer’s and who was the same age and sex, was from the same area, and had the same number of recorded healthcare visits.
In total, researchers examined data for 344,628 pairs. According to the study, 1,507 patients, as well as 823 control subjects, had been diagnosed with HSV-1.
Said a press release about the study’s result: “They found that an Alzheimer’s disease diagnosis was almost twice as common in people with an HPV-1 diagnosis in this database, and this association increased with older age.”
For people 65 or older, the average risk of developing Alzheimer’s is just under 11%. In contrast, the study reported that individuals with HSV-1 infections “ended up with a 19.8% risk.”
But for those who’d received HSV-1 infection treatment, there was some good news: That particular group of participants had a 17% risk reduction for an Alzheimer’s diagnosis.
Though there’s more work to be done in this field, the researchers concluded that their findings “place an even greater emphasis on viewing the prevention of herpesviruses as a public health priority.”
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