Information on outbreak case patients and their contacts is shown in table 1. The index patient (Case 1) was a 9-month-old boy born on November 23, 2010. On August 17, the patient developed fever and cough; on August 20, he developed bilateral weakness of lower extremities. The patient was hospitalized one month later (September 19), and the case was reported as having AFP on September 20. Epidemiologic investigations were conducted, and two inadequate stool specimens were obtained from the patient on September 20 and September 22. Type Pi Sabin-related poliovirus strains were isolated from two specimens with 5 nt VP1 substitutions.