AFP cases by week of paralysis onset and timing of SIAs in Xinjiang, 2011. WPV case clinical compatible polio cases non-polio AFP. WPV: wild poliovirus; AFP: acute flaccid paralysis. Note: The first SIAs was conducted among population <40 years of age in Southern Xinjiang, children < 15 years in Urumqi, and children <5 years in other prefectures. The second round of SIAs was conducted targeting children < 15 years in Southern Xinjiang and Urumqi, and children <5 years in other prefectures. The third round of SIAs targeted the same population as the first round of SIAs.