In Pakistan's poor northwest one of the newest victims, 13-month old Fariha, cried out as her 6-year-old sister Sana struggled to place her on the floor, mindful of her tiny legs wrapped in plastic braces.

A laborer's daughter, Fariha was infected six months after birth. She has to be carried everywhere. Twice a day her mother exercises her legs, medicines are provided free and a health worker visits occasionally. The braces were donated by a German clinic.

There are no guarantees that Fariha will fully recover. Most of the new polio cases in Pakistan are in the northwest, where an insurgency rages, making it difficult for health workers to reach tens of thousands of children.

Elsewhere in the world, a growing number of cases are being discovered and traced back to Pakistan and Nigeria. While the numbers are low today, WHO spokesman Oliver Rosenbauer warned that the disease can quickly regain strength.