Most people who live in rich countries assume [polio] is long gone and that it doesn’t kill or paralyze children anymore. But it is still a frightening presence in a number of places around the world. ... There are now just four countries where polio transmission has never been stopped: India, Nigeria, Pakistan, and Afghanistan. ... We are so close, but we have to finish the last leg of the journey. We need to bring the cases down to zero, maintain careful surveillance to ensure the virus is truly gone, and keep defenses up with polio vaccines until we’ve confirmed success.