Millions of Americans suffered from measles in the decades before the U.S. eliminated  the disease in 2000. But if an ongoing outbreak in New York state continues into next month, the U.S. could lose its "measles-free" status.

"As a global leader in public health, it is mortifying that (the U.S.) may lose its measles elimination status," said Dr. Paul Spiegel, director of the Johns Hopkins Center for Humanitarian Health. "The measles outbreaks should not have occurred as vaccination against measles is very effective."