Polio is an enduring torment for Zhang Yiming, who lives in a village in Jiangsu province. His younger brother wasn't given a polio vaccine in infancy and contracted the disease in early life, leaving the 30-something unable to walk or even stand without assistance.

The cost of treating the disease quickly ruined the family. "Throughout my five years at primary school, I wore a pair of my father's shoes. They were far too big, but my parents couldn't afford another pair," Zhang said.

Unkind comments from local children added to the family's distress. "Some of the kids shouted at us, saying my brother was an idiot because he couldn't move without a wheelchair," Zhang said.