Multiple sclerosis has been known as an individual disease since 1868, when it was identified by Jean-Martin Charcot, a French neurologist. Ever since then, the cause of multiple sclerosis has not been identified.
Theories as to the causes of multiple sclerosis came about during the twentieth century. Though scientists have not yet cracked open the true cause of this neurodegenerative disease, they are closer to understanding its pathogenesis.
One of the long-standing potential perpetrators is EBV, the Epstein-BarrVirus. There has long been a correlation between EBV and multiple sclerosis, and recently, some researchers took a long, hard look at that correlation to see if it is causation.
First, let us look at some of the other suspects.
A Combination of Causes
One of the first people in history to be identified as a victim of multiple sclerosis was Halldora from Iceland, who is described as having symptoms that match up with the disease.
Another woman from around the same time (a scant hundred years later), Saint Lidwina of Schiedam, in Holland, has also been identified as a potential multiple sclerosis sufferer.
Both were from northern Europe, and even today, multiple sclerosis seems to be tied to that geography. The further the population is from the equator, the higher the rate of multiple sclerosis within that population.
Originally this led to a hypothesis that some sort of 'Viking gene' was contributing to the disease, but that has not been proven, as joining in with geographical location, the season of birth has an effect as well. So, whether or not the person moves close to the equator, and when; when younger people move towards the equator, their risk of developing multiple sclerosis drops?
Vitamin D production, or a lack thereof, has been offered as an explanation for this phenomenon.
While multiple sclerosis is not considered a hereditary disease, there are genetic variations which can increase a person's level of risk for developing the disease. But they do not cause it. For example, if one identical twin is affected with multiple sclerosis, the other is affected only a third of the time.
Smoking has been linked with the disease. Stress and industrial solvents have been examined, but current research is not conclusive either way.
Another idea is that infectious agents such as microbes or viruses can cause multiple sclerosis. There are a number of viruses which can cause demyelination similar to what affects people with multiple sclerosis. One such virus, the Epstein-Barr Virus, is most linked with this neurodegenerative disease.
And it is this virus which the researchers examined.
Sean Burnard, Jeannette Lechner-Scott, and Rodney J. Scott undertook this quest. They published their results in the Multiple Sclerosis and Related Disorders Journal on June 9, 2017. They performed a systematic review of available literature, poring over existing data to sift through the noise and figure out of the connection between EBV and multiple sclerosis is causal or not.
The Prolific Epstein-Barr Virus
Epstein-Barr Virus is one of the most common viruses which infect people. It is also known as herpesvirus 4. It is transmitted through contact with liquids such as saliva, and from mother to child.
Thankfully, though over ninety percent of adults are infected or show signs of previous infection, it causes no trouble for most people. Either they will be completely asymptomatic, or only a minor and brief illness occurs.
It attacks the immune system directly, infecting your body's B cells as well as the epithelial cells which line your blood vessels and organs.
Children are most often infected and typically become asymptomatic, but if later adolescents or adults are infected then something called Infectious Mononucleosis can result. You may know it more simply as mono. Researchers tend to refer to it as IM.
Mono and Multiple Sclerosis
Previous research has indicated that people who come down with mono are more likely to develop multiple sclerosis later in life, on average fourteen years after getting mono. The relative risk increase was between two and four times; do note that this is relative risk, not absolute risk, and so is not as scary as it appears.
Between 90 and 95 percent of people worldwide have been infected with EBV. Among those with multiple sclerosis, however, over 99 percent of people have been infected with the virus.
Looking through the data, it appears as if the studies which showed under 100 percent infection rates used only a single detection method, which cannot provide one hundred percent accuracy. It is highly likely, therefore, that every single person with multiple sclerosis has been infected with EBV.
At least for adults. When looking at children, even controlling for methodology (the researchers are looking at the data of others, remember), not every child with multiple sclerosis tested positive for EBV infections.
Epstein-Barr Virus in the Brain
Signs of EBV infection often show up in autopsies of the brain and central nervous system of people with multiple sclerosis. Unfortunately, other deceased sufferers of the disease failed to show signs of EBV infection.
So, whether EBV causes multiple sclerosis by directly affecting the nervous system seems to be unsubstantiated. The researchers did note that this might be due to a lack of proper methodology in testing the samples, as the results form one study often did not fall in line with results in another study.
Perhaps, though, this is because EBV has causal factors outside the brain and central nervous system.
Outside Looking In
There is an idea called Molecular Mimicry. Basically, where sometimes invasive pathogenic cells look very similar to cells in the host body. So, when the autoimmune system develops a successful method of attacking those cells, antigens the very same mechanism by which the body defends itself then starts to attack the similar looking host cells.
The antigens which attack EBV, unfortunately, seem to also attack myelin basic protein, MBP. Multiple sclerosis involves demyelination, so these antigens could be to blame.
Very similar antigens are produced in response to other viruses, however. EBV does not have a monopoly on creating antigens which attack MBP.
There are other methods by which it is theorized EBV infections can attack the central nervous system. As EBV infects parts of the autoimmune system, it can hijack a working part of the system and so hide under the radar of the autoimmune system. The hijacked part will then produce excessive T cells, which then produce cytokines, which cause inflammation and can damage the nerves.
After looking at all this, and even more technical data, the researchers came to the conclusion that EBV is not a red herring. It more than just correlates with multiple sclerosis development, and mechanisms for causation are known.
However, just because the mechanisms are known, does not mean that if you become infected with EBV that you will develop multiple sclerosis. Otherwise, it would have been easier to pin down before now.
Also, other viruses can produce similar reactions that can also contribute to similar effects.
The researchers did point out that EBV settles into host cells randomly. This may be why EBV can lead to multiple sclerosis for some people and not for others.
So, overall, the Epstein-Barr Virus? Contributor to multiple sclerosis. But it is not a court sentence.
The Epstein-Barr Virus has a long history of being complicit in the development of multiple sclerosis. It seems to be tightly entwined with the disease; however, it is still not completely known how it may cause multiple sclerosis.
So between cause, contributor, or red herring, EBV seems to be a very strong contributor to multiple sclerosis. Thankfully it is not a complete cause, as the vast majority of Earth's population has been infected. Most people will not see any negative effects, though.