The World Health Organization says the northwestern Pakistani city of Peshawar has become the world's largest poliovirus reservoir.
The organization said in a news release on Friday that 90 percent of the current polio cases in the country are genetically linked to Peshawar, which is the provincial capital of Khyber Pakhtunkhwa province.
Dr. Elias Durry, who heads the organization's polio eradication efforts, says Peshawar doesn't necessarily have the most cases but most of the cases found around Pakistan can be traced back to the city.
The organization is calling for repeated vaccination campaigns to help eradicate the disease.
Pakistan is one of only three countries in the world where polio is still endemic.
The number of polio cases in Pakistan jumped from 58 in 2012 to 91 in 2013.