Empowering people affected by MS to live their best lives

Infectious Agents and Multiple Sclerosis

Scientists believe that a combination of factors causes multiple sclerosis. Specifically, they believe that MS occurs when people with the right combination of genes are exposed to some trigger in the environment.Studies have produced evidence that an infectious agent is involved in triggering MS. For instance:

The identical twin of someone living with MS, who shares virtually all the same genes, has only a 1 in 4 chance of developing the disease. This suggests that factors other than genetics are involved.
Data from epidemiological studies (studies that analyze the geographical, socioeconomic, genetic, environmental and other factors that may contribute to the development of MS) suggest that exposure to an infectious agent may be involved in triggering the disease.

There’s also evidence that the infectious agent that causes MS is a virus. For instance:

Ninety to 95% of people with MS have proteins in their spinal fluid. The presence of these proteins suggests inflammation of the central nervous system due to infection or another disease.

To date, researchers have not been able to identify a single virus as the trigger for MS. Several viruses have been studied, with Epstein-Barr virus showing the most evidence so far. But to prove that a particular virus causes MS, researchers must show that:

The virus is in the body before MS develops, and
The virus actually causes the disease and is not just happening alongside the disease.

The identical twin of someone living with MS, who shares virtually all the same genes, has only a 1 in 4 chance of developing the disease. This suggests that factors other than genetics are involved.
Data from epidemiological studies (studies that analyze the geographical, socioeconomic, genetic, environmental and other factors that may contribute to the development of MS) suggest that exposure to an infectious agent may be involved in triggering the disease.

There’s also evidence that the infectious agent that causes MS is a virus. For instance:

Ninety to 95% of people with MS have proteins in their spinal fluid. The presence of these proteins suggests inflammation of the central nervous system due to infection or another disease.

The virus is in the body before MS develops, and
The virus actually causes the disease and is not just happening alongside the disease.

Epstein-Barr virus (EBV) is very common, and most people are exposed to it in childhood, generally with mild or no symptoms. In adolescence and adulthood, it can cause infectious mononucleosis, a disease that increases the risk of later developing MS. The virus stays inactive in the body throughout a person’s lifetime and has been linked to certain cancers and autoimmune diseases. EBV can be reactivated by a trigger.Several studies led by Alberto Ascherio, M.D., Dr.P.H., (Harvard School of Public Health) provide the strongest evidence yet in the role of EBV in triggering MS. They show that EBV infection precedes both the symptoms of MS and nervous system damage and that becoming infected significantly increases the risk of developing MS in people whose genetic background, environment and lifestyle also add to their risk of getting MS.The studies found that:
Antibodies (immune proteins that indicate a person has been exposed) to EBV were much higher in people who eventually developed MS than in control samples of people who did not get the disease.
MS risk increased significantly following infection with EBV, thereby demonstrating that EBV was in the body before MS developed.
People with a specific immune-related gene and high levels of antibodies to EBV in their blood were 9 times more likely to develop MS than those without the gene and with low levels of the antibodies.
Current or previous smokers with the highest levels of EBV antibodies were 70% more likely to develop MS than those with neither risk factor.Learn more about the link between MS and the Epstein-Barr virus:
Ask an MS Expert: The Role of Epstein-Barr Virus in MS
Complex Link: Studies Show Epstein-Bar Virus as a Major Risk Factor for MS
Study Provides Strongest Evidence Yet for the Role of Epstein-Barr Virus in Triggering Multiple Sclerosis
Human herpes virus (HHV-6) may also be involved in MS — specifically by triggering relapses. A team in Spain found that HHV-6 antibodies reached their highest levels in people with MS two weeks before a relapse occurred. These researchers suggest that tracking HHV-6 antibodies may help to predict the clinical course of MS.

Viruses and Multiple Sclerosis

Infectious Agents and Multiple Sclerosis

The case for Epstein-Barr virus (EBV)

The case for human herpes virus 6 (HHV-6)