Multiple sclerosis (MS) is a disease that affects the brain and spinal cord. It happens when the body’s immune system mistakenly attacks the protective covering around nerves, called myelin. Over time, this damage makes it harder for the brain to send signals to the rest of the body.
This can lead to problems with movement, balance, and even thinking. Some people with MS eventually lose the ability to walk, while others may have milder symptoms. There is no cure for MS, and doctors still don’t fully understand what causes it.
MS is a relatively rare disease, but it affects about 2.8 million people worldwide. Scientists have long suspected that certain viruses might trigger the disease, but proving this has been difficult. Now, a large study from Harvard University has found strong evidence that a virus called Epstein-Barr virus (EBV) is the main cause of MS.
EBV is a very common virus. Most people get infected with it at some point in their lives, often in childhood. It can cause a mild illness or, in some cases, mononucleosis (also called “mono” or the “kissing disease”), which makes people feel very tired for weeks or even months.
Once a person is infected, EBV stays in the body forever, usually without causing any problems. Since almost everyone carries the virus but only a small number of people develop MS, it has been hard to prove that EBV is directly responsible for the disease.
To better understand the connection, researchers studied over 10 million young adults serving in the U.S. military. They focused on 955 people who were diagnosed with MS while in service. Because the military regularly collects blood samples from its members, scientists were able to check whether these individuals had been infected with EBV before they developed MS.
Their findings were striking. Almost every person who developed MS had been infected with EBV before their diagnosis. In fact, the risk of developing MS increased 32 times after someone got infected with EBV. Other viruses did not have the same effect.
The researchers also found that a key marker of nerve damage, called neurofilament light chain, only increased after EBV infection. This suggests that the virus plays a major role in triggering MS.
The delay between EBV infection and the first symptoms of MS—often about 10 years—may explain why the connection was not obvious before. Scientists believe that in the early stages, MS develops slowly and silently, making it hard to detect. It is also possible that the immune system’s response to EBV changes over time, leading to MS in some people but not others.
Currently, there is no way to prevent EBV infection, and there is no treatment to remove the virus from the body. However, this study raises hope that an EBV vaccine or antiviral drugs targeting the virus could one day prevent or even cure MS. Scientists are now working to develop these treatments.
This study, published in the journal Science, provides the strongest evidence yet that EBV is the leading cause of MS. If future research confirms these findings, it could change the way MS is treated and bring new hope to millions of people living with the disease.
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