Lessons from recent epidemiological studies in type 1 childhood diabetes

Recent studies have revealed that seasonality of onset of childhood insulin-dependent diabetes mellitus (IDDM) with a peak late in autumn and winter exists in populations with medium or high incidence of disease and parallels viral epidemics. In populations with low incidence no seasonality has been found, probably due to the development of tolerance towards the infectious agent(s). Analysis of the month of birth of children with IDDM showed a temporal shift with a peak in spring, but again only in populations with a medium or high incidence of childhood IDDM. This finding is suggestive of a transfer of virus infections from the mother to the fetus during the viral epidemic period. This unsymptomatic infection is assumed to cause the first pancreatic beta-cell damage which after subsequent damage leads to overt diabetes.