Clinical infections and multiple sclerosis: contribution from analytical epidemiology.

Epidemiological studies have suggested that exogenous factors may play a role in the etiology of multiple sclerosis and that the environmental component may be viral, but, as yet, there is insufficient evidence to draw any definite conclusions concerning any of the viruses so far proposed. The case-control approach failed to give any definitive conclusion. While the frequency of each common childhood illness is not significantly different between cases and controls, there are more consistent data suggesting that cases do report a later age at infections: this applies particularly to measles, rubella, mumps and EBV infection. Several studies have proved that viral or bacterial infections or reactivations could trigger the clinical attacks in relapsing-remitting MS.