statistics, real statistics, and damn statistics
Part of the increase, over time, of the statistical numbers for cases of GBS has to do with population increase. General research shows ~2-3 cases/yr for every 100,000 people (and yes, there are MANY variations on this number). Since the disease generally hits people in a certain age range (say, 30-70) and the probabilities change with age within this region, the statistical probabilities are not uniform. Thus, a great deal of research now says that ~10/100,000 people will have GBS during a lifetime, and that number is growing. But also of note is that the population is growing, and people are living longer, so the statistical probability is not static.
Just something to think about. Consider, there are more people alive on the earth today, than have ever died throughout history as we know it.