CHARLOTTE, N.C. — Researchers report a common virus may be the leading cause of multiple sclerosis.

The Harvard University study examined about 800 people who developed multiple sclerosis

It found that more than 99% were infected with the Epstein-Barr virus, which often causes the common illness mononucleosis

Researchers believe other factors also contribute to MS. Many people who obtain the Epstein-Barr virus do not develop MS

MS advocates hope this study could lead to new treatments or a vaccine.

Carol Hunley tries to do light exercise a few times a week. Her goal is to build and maintain strength. She has multiple sclerosis, which is an inflammatory disease that attacks the nervous system.

“I feel comfortable on the treadmill because I can hold on,” Hunley said.

It’s easy for her to lose her balance. It’s why she also wears a walk-aid on her right knee.

“It senses that I am taking a step and picks up my foot,” Hunley said. “It stimulates my muscles to my angle that picks up the foot.”

Hunley developed the illness several years ago. She always wondered what could have caused it. Then, she came across a recent study which showed the Epstein-Barr virus may be the leading cause.

“I just thought, 'uh-huh,'” Hunley said. “I had severe mono when I was in college. That could have been a trigger.”“I just thought, 'uh-huh,'” Hunley said. “I had severe mono when I was in college. That could have been a trigger.”

According to the CDC, Epstein-Barr virus is the most common cause of infectious mononucleosis, but other viruses can also cause this disease as well. Mark Allegretta is the vice president of research for the National Multiple Sclerosis Society. He says the virus can leave a lifetime infection in the host.

“The concept is molecular mimicry,” Allegretta said. “When an infectious disease generates an immune response, for some subjects who are already at risk for developing an auto-immune disease, in those subjects it actually targets the central nervous system. In this case it’s called glycan.”

Doctors hope this new information could help create more therapies, which target the Epstein-Barr virus so it doesn’t progress. It could also entice pharmaceutical companies to develop a vaccine. But Allegretta said there could be some challenges with this research.

“You can imagine that how you generate an immune response through a vaccine could be very important,” Allegretta said. “You wouldn’t want to make a vaccine that could make MS worse.”

Epstein-Barr virus alone doesn’t necessarily cause multiple sclerosis. Allegretta says there are usually other contributing factors. One is vitamin D deficiency. 

“Back in 2015 I started to take vitamin D, that was when I was diagnosed with MS," Hunley said.

Hunley says it’s not clear if this study could directly help her. But she believes it could help many generations to come.

“My one daughter had mono, which is associated with the Epstein-Barr virus,” Hunley said. “So now she knows to look for potential indications and systems. It gives me a lot of hope.”