SMALLPOX WAS ONCE the world's most feared disease. It killed or disfigured millions of people. Now, according to the doctors who have been hunting it down, smallpox is gone. It will no longer plague mankind.

The last known natural case of smallpox occurred two years ago in Somalia, where more than 2,500 cases had developed earlier that year. The last victim, a hospital cook, was isolated, and all those who might have come in contact with him were vaccinated. There have been no more cases in Somalia. Except for two cases in England that resulted from faulty handling of smallpox virus in a laboratory, no other cases have been reported. Except for laboratory samples, doctors believe the virus has been destroyed.

The credit for the drive that led to this remarkable belief goes to the World Health Organization. WHO's medical teams, led by Dr. Donald Henderson, set out in 1966 to eliminate smallpox within 10 years. Few who participated in setting that goal believed there was any chance of reaching it. But the goal turned out to be only slightly optimistic, because governments everywhere cooperated in the effort and a new freeze-dried vaccine made mass vaccinations possible.

The impact of smallpox over the years has been staggering. The disease swept Europe repeatedly, and as recently as 1919 more than 3,500 people died from it in Spain alone. Some historians credit it for the Europeans' easy conquest of North America because the new disease carried in from Europe so ravaged the American Indian population.

If smallpox is now gone, as the doctors believe -- and there is every reason to think they are right -- the world is a better place to live because it finally organized itself to take full advantage of the discovery Edward Jenner made in England 183 years ago. That -- the banding together of people everywhere, without regard to politics or national glory, to defeat a common enemy -- is the true miracle.