Multiple sclerosis: link with earlier infection just got stronger – The Jerusalem Post

We found that glandular fever between ages 11 and 19 was associated with a significantly increased MS risk after age 20 years, in an analysis that compared siblings with each other in every family separately, and then the results were combined. This design was to make sure the results are not because people susceptible to MS are also more likely to have more severe infections because of this susceptibility. The results confirm that glandular fever, and almost certainly other infections, are important risk factors for MS and able to trigger the disease.
The new study also made it possible to look in greater detail at when an infection is more likely to trigger MS. Glandular fever in earlier childhood was less of a risk for MS than when it occurred after age 11 years. The highest risk for MS was seen for infections between ages 11 and 15 years (around the time of puberty), with the risk dropping with increasing age and almost completely disappearing by age 25. Changes in the brain and immune system as people age may help explain this.
Even though glandular fever may be triggering MS, most often around puberty, it can be many years before MS is diagnosed. Many who had the infection between ages 11 and 15 years did not have an MS diagnosis until after they were 30. This is because the damage to the brain caused by MS develops slowly until it makes someone sick enough to receive a diagnosis of MS.
Glandular fever during the teenage years may trigger MS because it can get into the brain. And the damage it causes to nerve cells may cause the immune system to start attacking a part of the nerves that insulates them – called the myelin sheath.

Source: Multiple sclerosis: link with earlier infection just got stronger – The Jerusalem Post