A new study from Harvard University has found powerful evidence that a common virus, called Epstein-Barr virus (EBV), is likely the main cause of multiple sclerosis (MS), a serious disease of the nervous system that affects about 2.8 million people around the world. This discovery could change how we understand, prevent, and possibly even cure MS in the future.
Multiple sclerosis is a long-term disease that damages the brain and spinal cord. It happens when the immune system attacks the protective covering (called myelin) around nerve cells. This can lead to a wide range of problems, such as trouble walking, vision issues, and memory problems. So far, doctors don’t know exactly what causes MS, and there’s no cure.
For many years, scientists believed that the Epstein-Barr virus might play a role in causing MS, but they didn’t have solid proof—until now.
EBV is very common. Around 95% of adults have been infected with it, usually during childhood or early adulthood. It can cause mild symptoms or lead to a condition known as “mono” or “kissing disease.” Once someone is infected, the virus stays in their body for life.
Because EBV is so common, and MS is quite rare, it has been hard to show that EBV actually causes MS and isn’t just a coincidence.
To figure this out, Harvard researchers looked at health records and blood samples from more than 10 million young adults who served in the U.S. military. Among them, 955 people developed MS during their years of service.
These service members had their blood tested every two years, so the researchers were able to track when each person became infected with EBV and when they started showing signs of MS.
The results were striking. People who got infected with EBV were 32 times more likely to develop MS later on. No other virus had this kind of effect. Even more interesting, a marker in the blood called neurofilament light chain—which shows damage to nerve cells—only went up after someone was infected with EBV. This means the damage linked to MS began after the virus showed up.
These findings point clearly to EBV as the main cause of MS. Other known risk factors, like genetics or lifestyle, couldn’t explain the strong connection found in this study.
The researchers believe the delay between EBV infection and MS symptoms—often around 10 years—may be due to two things: first, MS can start silently, with no clear symptoms at the beginning; and second, EBV might slowly affect the immune system in a way that leads to MS over time.
Right now, there is no way to prevent or treat EBV. But this study gives new hope. If scientists can develop a vaccine to stop EBV infection, or create drugs that target the virus, it might be possible to prevent MS entirely—or even cure it in some cases.
The study was led by Dr. Alberto Ascherio and published in the journal Science. It adds strong support to the idea that EBV isn’t just connected to MS—it may actually be the cause.
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