Polio vaccinators sit with boxes of the vaccine in a bus as they leave to administer it to children in different parts of Karachi October 21, 2014. Taliban militants have long been the scourge of Pakistan's polio vaccination campaign, attacking aid workers and the police who protect them as they distribute doses to children. But experts say there is another reason for the sharp spike in cases of the crippling disease in Pakistan this year - government mismanagement. (REUTERS/Akhtar Soomro)
A health official in Pakistan says four new polio cases have been detected in the country, bringing the number of children affected by the crippling disease this year to 276.