What is polio? Why are authorities worried about it spreading in London and New York City? - ABC News

Polio is back in the global conversation again over concerns the disease is spreading in London and New York. Experts say under-vaccination is behind it.

Polio is back in the global conversation again over concerns the disease is spreading in London and New York.  Let's get you up to speed on what's been happening and answer your basic questions abou… [+5180 chars]

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