Chicago O'Hare is one of the world's busiest airports.

VOA: special.2009.01.12

Still,W.H.O.officials continue to report new cases across the world.

VOA: special.2009.07.14

The W.H.O.says since 1988, more than two billion children around the world have been immunized against polio.

VOA: standard.2010.08.02