Never before in the history of polio have so few children contracted the virus, but the international community cannot rest until the number of cases is zero, the UN Children's Fund (UNICEF) said on the eve of World Polio Day.

"Progress to end polio is real and dramatic, with now just two countries in the world where the poliovirus has never been interrupted: Afghanistan and Pakistan," Xinhua news agency quoted Peter Crowley, head of the Polio Unit at UNICEF as saying on Friday.

"But — and it is a big but — until all children everywhere are consistently and routinely immunised against polio, the threat remains," Crowley said.

World Polio Day was established for annual observance on October 24 by Rotary International more than a decade ago to commemorate the fight against poliomyelitis.

Widespread use of poliovirus vaccine led to an increasing number of polio-free countries and to the establishment of the Global Polio Eradication Initiative (GPEI) in 1988.

As of October 14, a total of 243 polio cases had been reported in 2014, with 92 percent of the cases reported from Nigeria, Afghanistan, and Pakistan, the only three countries where transmission of indigenous wild poliovirus has continued uninterrupted.