Polio is most often transmitted by eating or drinking contaminated food or water. The virus is passed in the feces of an infected person. If the water supply is contaminated with human excrement, it will act as a reservoir for future infections.

Improving sanitation on a large scale has failed to eradicate this infection in certain parts of the world where living standards are poor. The only hope of getting rid of this disease once and for all is through a comprehensive childhood vaccination program in those remaining countries that harbor the polio virus.