Association of influenza incidence with multiple sclerosis onset.

The aim of this study was to investigate the environmental factors influencing the tangible changes in the incidence of multiple sclerosis (MS) over a period of the past 30 years in the town Gniezno, Poland. We analysed many environmental factors to which the whole population was exposed in the respective period. The following factors were considered: viral infections (influenza, measles, varicella, rubella, mumps), atmospheric air pollution and climate conditions. A positive correlation has been found between the incidence of influenza and the incidence of MS in the same year (r = 0.37; p = 0.04) as well as with the MS incidence assessed after 5 years (r = 0.64; p = 0.0005). No significant correlation has been found between the incidence of MS and other investigated environmental factors. These results support the hypothesis that influenza infection could precipitate MS onset.