The World Health Organization (WHO) says the northwestern Pakistani city of Peshawar is the "largest reservoir of endemic polio viruses in the world."
The WHO said in a statement on January 17 that more than 90 percent of the current cases of polio are linked to Peshawar and that 12 out of 13 registered cases in neighboring Afghanistan were also connected to the Pakistani city.
Eighty-three of 91 cases of polio registered in Pakistan last year were in, or could be traced back to Peshawar.
There were only 58 cases recorded in Pakistan in 2012.
Pakistan's antipolio vaccination campaign has been marked by violence against health workers and volunteers attempting to administer antipolio drops.
Militants have called the campaign anti-Islamic and health workers of being spies for the United States.
Based on reporting by Reuters, AFP, and dpa