The following article discusses the theory of an MS trait which is triggered usually by a virus in adolescence.
I corresponded with Dr Chadhuri (who penned the Tysabri article) and he suggested that the way to prevent MS was an EBV vaccine. By coincidence, one of the UK newspapers on Tuesday (Evening Standard) discussed cancer vaccines and mentioned work on an EBV vaccine.
One could theorise that children today become exposed earlier to viruses such as EBV than a few decades ago (more living in cities, more travel / use packed public transport) which may account for the increase in MS in children (in addition to better diagnosis).
I have been invited to attend an EBV workshop being run by the UK MS Society in mid-May so it will be interesting to find out what research is being undertaken.
In the US research has shown that it is the children of parents who have moved from other countries who are seeing the greatest increas in a dx of MS. This might suggest that something protected them in the other countries (lack of exposure to certain viruses?)
MS really is a very complex disease. But I think they are getting nearer to unravelling it (but on my bad days, I think its like Stevie Wonder being able to do a Rubik's cube)