Below is an instruction from Human. Write a response.
    ### Instruction:
    How many people are affected by Guillain-Barr syndrome ?
    ### Response:
    The prevalence of Guillain-Barr syndrome is estimated to be 6 to 40 cases per 1 million people. The occurrence of the different types of Guillain-Barr syndrome varies across regions. AIDP is the most common type in North America and Europe, accounting for approximately 90 percent of cases of Guillain-Barr syndrome in those regions.
    