One of the most contagious viral diseases known, measles infects 30 million to 40 million children per year. Nutritious diets and excellent health care prevent all but a very few deaths in rich countries; but in the developing world, measles often paves the way for pneumonia, diarrhea, and other infections, killing more than 750,000 children last year.

In 1994, ministers of health in North and South America launched an all-out war against measles, which that year infected about 25,000 people. They used a threefold strategy: an initial, massive immunization campaign for all children under 15, follow-up campaigns every 4 years for kids under 4, and routine shots for everyone at age 1. The campaign had several setbacks; a major outbreak in 1997 caused more than 52,000 cases in Brazil, for instance. But overall, a downward trend prevailed, and on 20 September, the steady trickle of new cases came to a halt.

Experts warn that the virus could still be hiding in remote and politically turbulent areas where surveillance is difficult. What't more, so-called imported cases will still occur--often from other developed countries, such as Japan and Germany, where vaccine coverage is lower. So staying vigilant and keeping vaccination rates high will be essential, says Ciro de Quadraos, a former head of the division of vaccines and immunization at the Pan American Health Organization (PAHO) in Washington, D.C.

Still, the dramatic decline since 1994 sets an inspiring example for the rest of the world, says Edward Hoekstra, coordinator of UNICEF's Global Measles Program. During the Special Session on Children in 2000, United Nations member states committed themselves to cutting the number of measles deaths in half (from the 1999 level) by 2005; if the goal proves feasible, the U.N. might consider a global eradication effort. "There's no reason why this success could not be repeated elsewhere," Hoekstra says.

--MARTIN ENSERINK