A Common Virus Could Be the Hidden Trigger for Multiple Sclerosis

Multiple sclerosis (MS) is a serious condition that impacts the brain and spinal cord. It occurs when the immune system mistakenly targets the body’s own nerve cells.

This damage disrupts how the brain communicates signals throughout the body. People with MS often face challenges with movement, vision, balance, and cognition. In severe cases, it can result in lasting disability and may even reduce lifespan.

Globally, approximately 2.8 million individuals are living with MS. Researchers have long sought to understand its causes, but clear answers have been elusive. Various factors—such as genetic predisposition and environmental influences—have been proposed, yet no definitive cause has been identified.

A groundbreaking study from Harvard University now offers compelling evidence pointing to a common virus — Epstein-Barr virus (EBV) — as a potential primary cause of MS.

EBV is highly prevalent, with about 95% of adults worldwide having been infected at some stage in their lives. It is best known for causing infectious mononucleosis, often called “mono” or the “kissing disease.” Once infected, the virus remains dormant in the body for life, typically in a passive state.

Due to its widespread nature, establishing EBV as the culprit behind MS has been challenging. Many individuals infected with EBV never develop MS, and symptoms often emerge many years after initial infection. This lengthy lag complicates efforts to connect the two directly.

The new research overcame these challenges by analyzing a vast and detailed dataset. Researchers followed over 10 million young adults serving in the U.S. military, who regularly provided blood samples as part of their service, enabling tracking of infections over time.

Within this group, 955 individuals were later diagnosed with MS. The scientists meticulously examined their blood samples, collected every two years, to pinpoint when they contracted EBV relative to their MS diagnosis.

The results were striking. The risk of developing MS increased by 32-fold after EBV infection. This represents a significant correlation. In contrast, infections with other viruses did not show any meaningful association with MS.

The team also measured a blood marker called neurofilament light chain, which is released when nerve cells are damaged. They observed that levels of this marker rose only after EBV infection, hinting that the virus may initiate nerve damage characteristic of MS.

Collectively, these findings strongly suggest that EBV isn’t just linked to MS but likely plays a central role in causing it. The researchers theorize that following EBV infection, the immune system may gradually undergo changes, eventually turning against the body’s own nerves.

The delay between infection and the onset of symptoms could be due to a slow, insidious development process—nerve damage might begin years before any noticeable signs of MS appear.

This discovery is significant because it paves the way for new strategies to prevent and treat MS. Currently, no methods exist to prevent EBV infection, nor is there a cure for MS. But if EBV is the main cause, targeting the virus might protect against the disease altogether.

Looking ahead, scientists may develop vaccines to shield people from EBV or antiviral therapies that could be administered to infected individuals to reduce the risk or halt the progression of MS. Such advancements could transform how the disease is prevented and managed.

This research was led by Alberto Ascherio and published in the journal Science. It represents one of the strongest pieces of evidence to date linking a virus to a major chronic illness.

Although further studies are needed, this breakthrough offers new hope to millions affected by MS. It suggests that what once appeared to be an inscrutable disease might have a clear and preventable root cause.