Multiple sclerosis, often called MS, is one of the most complex and challenging diseases affecting the brain and nervous system.
It is a lifelong condition that can gradually damage a person’s ability to move, think, see, and carry out everyday activities.
Although treatments can help manage symptoms and slow the disease, there is currently no cure. For decades, scientists have searched for the root cause of MS, hoping that understanding what triggers the disease could lead to better ways to prevent and treat it.
Now, a major study from Harvard University has provided some of the strongest evidence yet that a common virus may be the leading cause of multiple sclerosis. The findings could change how scientists think about the disease and open the door to new strategies for prevention.
Multiple sclerosis is an autoimmune disease. This means the body’s immune system mistakenly attacks healthy tissues instead of protecting them. In people with MS, the immune system targets a protective covering called myelin.
Myelin surrounds nerve fibers in the brain and spinal cord and acts like insulation around electrical wires. It helps nerve signals travel quickly and efficiently throughout the body.
When myelin becomes damaged, nerve signals slow down or become disrupted. As a result, people with MS can develop a wide range of symptoms.
These may include muscle weakness, numbness, balance problems, vision changes, fatigue, memory difficulties, and problems with coordination. Symptoms vary greatly from person to person. Some people experience mild symptoms for many years, while others develop severe disabilities over time.
Today, about 2.8 million people worldwide are living with multiple sclerosis. The disease often begins in young adulthood and can have a major impact on quality of life, employment, and independence.
For many years, researchers have suspected that infections might play a role in triggering MS. One virus in particular has attracted attention: Epstein-Barr virus, commonly known as EBV.
EBV is one of the most common viruses in the world. It belongs to the herpes virus family and infects approximately 95% of adults globally. Most people become infected during childhood or adolescence. Once a person is infected, the virus remains in the body for life.
Many EBV infections cause few or no symptoms. However, the virus is best known for causing infectious mononucleosis, often called “mono” or the “kissing disease.” Symptoms of mono can include fatigue, fever, sore throat, and swollen lymph nodes.
Scientists have long noticed a possible connection between EBV and multiple sclerosis. However, proving that the virus actually causes the disease has been extremely difficult. Because almost everyone is infected with EBV, it has been challenging to determine whether the virus is simply associated with MS or is directly responsible for triggering it.
Another challenge is timing. Symptoms of MS often appear many years after a person first becomes infected with EBV. In many cases, the gap can be around a decade or longer. This long delay makes it difficult to track the relationship between infection and disease development.
To investigate the question more carefully, researchers led by Dr. Alberto Ascherio conducted one of the largest studies ever performed on the topic. The team examined health records from more than 10 million young adults serving in the United States military.
This unique population provided a valuable opportunity because military personnel regularly provide blood samples during their service. These blood samples are stored and can be analyzed later, allowing researchers to track infections over time.
Among the more than 10 million service members studied, 955 people were diagnosed with multiple sclerosis during their military careers. Because blood samples had been collected every two years, the researchers could determine when individuals became infected with EBV and whether the infection occurred before the onset of MS.
The results were remarkable. People who became infected with EBV were found to be 32 times more likely to develop multiple sclerosis than people who were not infected. No other virus showed a similar increase in risk.
The researchers also looked for signs of nerve damage in blood samples. They measured levels of a protein called neurofilament light chain, which is released when nerve cells are injured. Elevated levels of this protein are considered a marker of damage to the nervous system.
The study found that neurofilament light chain levels increased only after people became infected with EBV. This suggests that nerve damage associated with multiple sclerosis begins after the viral infection occurs.
Taken together, the findings provide powerful evidence that Epstein-Barr virus plays a central role in causing multiple sclerosis. According to the researchers, the results are difficult to explain using any other known risk factor.
The study also helps explain why MS develops so slowly. Scientists believe that the virus may trigger complex changes in the immune system that gradually damage the nervous system over many years before symptoms become noticeable.
The discovery has important implications for the future. If EBV is truly the main cause of multiple sclerosis, preventing or treating the virus could potentially prevent many cases of the disease. Currently, there are no approved vaccines that prevent EBV infection, and there are limited options for treating the virus once it becomes established in the body.
However, several research groups are already working on EBV vaccines and new antiviral treatments. If these efforts succeed, they could potentially reduce the risk of developing MS in future generations.
Experts caution that more research is still needed to understand exactly how EBV triggers multiple sclerosis and why only a small percentage of infected people develop the disease. Genetic factors, environmental influences, vitamin D levels, smoking, and other factors may also contribute to risk.
Nevertheless, the study represents a major breakthrough in MS research. After decades of uncertainty, scientists now have strong evidence pointing to a likely cause of the disease.
The findings offer hope that future vaccines, antiviral medicines, and targeted therapies could one day prevent multiple sclerosis before it starts, improving the lives of millions of people around the world.
The study was led by Dr. Alberto Ascherio and published in the journal Science.
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