Teenage 'kissing disease' could trigger multiple sclerosis — and scientists say one shot could end both forever

• A common virus, called EBV, might lead to multiple sclerosis later in life, scientists say.
• EBV causes mono, the "kissing disease," and can trigger a heightened immune response in teens.

Christian Denis ditched high school to stay home and sleep.

"I just remember my dad always being like: 'Are you on drugs? Are you okay? What are you doing?'"

"No!" Denis would respond. "I'm just tired."

The issue lasted through one whole summer between his freshman and sophomore year, when the formerly athletic teen didn't play any soccer or basketball with his friends. And then, suddenly, it was all over, and he was back to normal — at least for a while.

Denis, now 39, never got a diagnosis, but he's almost positive that 1999 was the year he and his girlfriend both had mononucleosis, what's often referred to as the teen "kissing disease."

Three years later, at 19, Denis started developing new and strange symptoms — double vision, and trouble pointing, lifting, and grabbing things. He was soon diagnosed with multiple sclerosis, a progressive, chronic disease of the brain and spinal cord that can cause a wide variety of symptoms including paralysis and cognitive dysfunction.

But it's only recently that scientists have zeroed in on the fact that Denis's high school mono infection — triggered by the common Epstein-Barr virus (EBV) — was almost certainly one critical factor that led to his MS diagnosis. Researchers are hoping a better understanding of this connection could lead to improved treatments — or even help eradicate MS for good.

A compelling link between viruses and chronic diseases

The idea that a short-lived viral illness can trigger chronic diseases years later is still a relatively new one in medicine.

"It's probably a bold statement, but it's likely to be true that almost all autoimmune diseases are triggered by a microbe, usually a virus," Dr. Lawrence Steinman, a neurology and MS expert at Stanford, told Insider.

EBV, specifically, is a virus that's been linked to multiple health issues including Hodgkin's lymphomas and rheumatoid arthritis.

Harvard professor Alberto Ascherio has studied more than 10 million US military members, and discovered that their risk of developing MS increases 32-fold after an EBV infection. That's on par with how smoking causes cancer.

"This is a big step because it suggests that most MS cases could be prevented by stopping EBV infection, and that targeting EBV could lead to the discovery of a cure for MS," Ascherio said in a press release when his blockbuster study came out in January.

But simply knowing that EBV likely triggers MS isn't the whole story. EBV is a virus most of us will get at some point by our mid-20s. Experts estimate that more than 90% of people worldwide have had EBV — and yet fewer than 0.5% of us will develop MS.

"It's certainly necessary to have an EBV infection," Steinman said. "But what else does it take?"

EBV is a likely trigger for MS — but the virus doesn't act alone

Most EBV infections young children get are completely asymptomatic, and those infections don't necessarily up the odds of developing MS.

The more exhausting, symptomatic infectious mononucleosis young adults with EBV can get is far more likely to trigger an exaggerated immune response, and that puts teens who've had mono at higher risk of developing MS.

Through his research, Steinman has discovered two additional factors that likely contribute to MS development. The first is how well a person's EBV antibodies bind to proteins inside the body at specific moments, and the second is genetic.

Steinman says researchers still don't understand all the other "subtle mechanisms involved" in the development of MS, but they're getting closer than ever with these recent discoveries.

Current treatments for MS are risky and expensive

While some MS patients only experience mild, sporadic episodes of clumsiness, muscle stiffness and spasms, others experience paralysis, cognitive dysfunction, and incontinence issues. Though there are many drugs available to help control the disease, there is no cure for MS, which affects about 1 million people across the US.

Denis takes about a dozen pills a year to control his MS, and uses a wheelchair and special hand controls in the car to get around.

Others MS patients, like Roxane Beygi, have gone through more intensive treatments. Beygi was diagnosed with MS at age 14, also after suffering a bout of extreme fatigue months prior.

Beygi decided to go through a personalized hematopoietic stem cell transplant to treat her MS symptoms, a process that is risky, costly, and is only performed by one physician in the US. Twelve years later, she only has one lingering issue: really bad handwriting.

"To me, it's the closest thing to a cure for MS that is available right now," the law school student said.

But a stem cell treatment is out of reach for most MS patients.

Soon, preventing MS could be as simple as a shot

Learning more about how and when EBV infections might trigger the development of MS has opened new avenues for prevention and treatment.

Leading MS experts, including Steinman and Ascherio, think that a vaccine against EBV could make MS a bygone disease. Even if they don't fully understand all the complex molecular mechanisms that might be involved in how people develop the debilitating central nervous system issue, they could potentially still end it by giving kids an EBV vaccine. Moderna has one in early-stage trials now.

Discoveries about the connection between EBV and MS could also open the door for new types of preventive treatments for high-risk patients who get mono. There could be antiviral drugs developed, similar to Tamiflu or Paxlovid, to help patients with risk factors for MS get through the illness faster and safer.

"We take antivirals for other herpes virus infections, including shingles," Steinman said. "So why not for mononucleosis?"

Both experts say it's exciting to think about how such a complicated and incurable disease could be stopped with these kinds of comparatively simpler, more preventative methods.

Patients are thrilled as well.

"The idea of it sounds amazing," Denis said of the thought of ending MS for future generations.