 Polio in Pakistan resurged in the latter part of the year.Cases in Afghanistan represented two transmission clusters, one in Kandahar, Urozgan and Helmand Provinces in the south, the other in the adjacent Nuristan, Kunar and Nangarhar Provinces in the northeast, on the Pakistani border.Virus involved in several Afghanistan cases had a closest relative in Pakistan, suggesting significant trans-border spread, but the majority represented spread within Afghanistan.