Tremendous progress had been made, but the world is not yet polio-free. The poliovirus knows no borders and can spread from an endemic country into polio-free areas. No child is safe from the crippling, sometimes fatal, disease as long as one case of polio remains in the world. The last 1 percent of polio cases are the most difficult to prevent because the virus lingers in some of the hardest-to-reach areas on earth. Increased support from governments of the world, and donor and polio-affected countries, is essential to the success of the Global Polio Eradication Initiative.