Multiple sclerosis (MS) is a long-term disease that affects the brain and spinal cord. It happens when the body’s immune system mistakenly attacks myelin, the protective covering around nerve fibers.
As this damage builds up, messages between the brain and the rest of the body become slower or stop completely, leading to problems with movement, vision, balance, and thinking.
Around 2.8 million people around the world are living with MS. The disease often develops in young adults and can gradually lead to disability. Although doctors have known about MS for many years, its exact cause has remained one of the biggest unanswered questions in medicine.
A major new study from Harvard University has now provided strong evidence that infection with the Epstein-Barr virus, also known as EBV, is the main cause of multiple sclerosis. The findings could change how scientists think about preventing and treating the disease. The research was published in the journal Science.
EBV is a very common virus from the herpes virus family. It is best known for causing infectious mononucleosis, sometimes called glandular fever or the kissing disease. About 95% of adults become infected at some point in their lives, and the virus stays in the body for life, usually without causing ongoing symptoms.
For many years, researchers suspected that EBV might be linked to MS. However, proving the connection was difficult because almost everyone catches the virus, while only a small number of people develop MS. In addition, MS symptoms often appear about 10 years after the initial infection.
To investigate the link, researchers studied the health records of more than 10 million young adults serving in the U.S. military. During the study, 955 people developed multiple sclerosis. The scientists also examined blood samples collected every two years, allowing them to see exactly when EBV infection occurred.
The results were striking. People who became infected with EBV had a 32-times higher risk of developing MS than those who had not yet been infected. Other viral infections did not show the same effect, making EBV stand out as the strongest known risk factor for the disease.
The researchers also measured a protein called neurofilament light chain, which is released when nerve cells are damaged. Levels of this protein increased only after EBV infection, showing that nerve damage began after the virus entered the body. This finding provides even stronger evidence that EBV plays a direct role in causing MS.
The scientists believe the long delay between infection and symptoms may happen because the disease develops slowly over many years. Changes in the immune system and early nerve damage may begin long before a person notices any signs of illness.
This discovery could lead to completely new ways of fighting multiple sclerosis. Scientists are now working on vaccines and antiviral medicines that target EBV. If these treatments can stop EBV infection, they may also prevent many future cases of MS or help slow the disease after it begins.
Although more research is still needed, this study offers new hope for millions of people affected by multiple sclerosis. It suggests that preventing one very common viral infection could dramatically reduce the number of people who develop this life-changing disease. The research was led by Alberto Ascherio and published in Science.
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