MS is not something you can catch or can get from direct contact. It occurs when 'something' makes the person's own immune system start to attack the nerve pathways in their body.
Quite what starts these attacks in MS is not yet known. Various possible triggers have been considered, the commonest being :
Various infections; chicken pox, measles, mumps, canine distemper and a number of herpes viruses have all been considered.
MS is occasionally found in families and therefore there is likely to be a genetic component - but MS is not considered to be a hereditary condition like haemophilia, and in identical twins one can develop MS and the other twin be disease free.
MS is more common in temperate climates, further away from the equator eg Canada and Scotland . This has made people think that lack of sunlight and hence lack of Vitamin D production, could be a trigger.
There are a number of studies and theories around diet, with 'fatty'diets thought to be harmful and diets high in fish thought to be beneficial.
A 2018 study found that long term exposure to solvents, such as those in paints, varnishes and glues could be a significant trigger.
As these individual triggers affect many people who are quite healthy, it is likely that a number of triggers need to be present for someone to actually develop MS. Equally some people with MS may have no 'identifiable' triggers.
Whatever the trigger, the result is that your body starts to attack the myelin, a fatty substance which surrounds nerves and nerve cells and which acts as an insulation, helping the nerves to transmit messages smoothly. In MS, this myelin covering becomes inflamed, and each episode of inflammation causes scarring. This scarring means nerve impulses are interrupted or muddled when travelling from one part of the nervous system to another; this may be within the brain itself (e.g difficulty with memory) or from the brain to a different part of the body (e.g numbness in one leg). As any nerve in the body can be affected, any number of symptoms may result, but some of the commonest are blurring of vision, unsteadiness, numbness, slurred speech and urinary problems.
For those who have the relapsing-remitting form of MS(RRMS), a new symptom may occur with a relapse and then recover. However with repeated episodes the recovery may be less complete so that over time some symptoms persist and may become permanent. As MS can present in so many different ways, it can often take a while to reach a definite diagnosis. Furthermore there is no clear way of identifying how the disease is going to affect an individual as no two people with MS present in the same way, or necessarily display the same course of the illness.