I have always found MS fascinating mainly owing to the fact that it appears to affect certain populations and not others. If you live in Tasmania which is on the most southern end of Australia you have a high risk whereas in the tropics you have a low risk of developing the disease.
But if you were born and raised at the higher latitudes of Tasmania but moved to an area of low incidence of MS before 15 years old you lose your 'high risk status'.
If you live in the tropics you are low risk, it seems like exposure to sun (and it has to be all year round exposure) seems to stop the disease.
I love the sun and hate winter, I think it's great for the immune system, people just don't get sick in summer! moving to the sun Australia from the UK when I was four cured my eczema.