Atlanta - South Sudan has gone 15 months without a single reported case of Guinea worm disease, the nation's health minister said on Wednesday, suggesting a major victory for global health officials trying to eliminate the debilitating affliction.Also, the Carter Centre said only 30 cases were reported last year in isolated areas of Ethiopia and Chad. That's a real achievement for efforts to eradicate a disease that only 30 years ago affected 3.5 million people a year in 21 countries across Africa and Asia.Contracted by drinking infected water, Guinea worm disease affects some of the world's most vulnerable people. The 3-foot-long (meter-long) worm is asymptomatic and incubates in people for up to a year before painfully emerging, often through extremely sensitive parts of the body.Unlike other diseases that are controlled by medicines or vaccines, Guinea worm can be eradicated through education, by training people to filter and drink clean water.South Sudan was one of nine countries still affected when its eradication program began in 2006. At the time, the disease was endemic in more than 3 000 villages, and the country tallied more than 20 500 cases.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. South Sudan's progress against Guinea worm, announced at the centre by its health minister, Dr. Riek Gai Kok, is being touted as one of the few successes to emerge from the young nation while it battles a five-year civil war, starvation and human rights atrocities.The global campaign to wipe out guinea worm was launched by the World Health Organisation and the US Centres for Disease Control and Prevention. Former US President Jimmy Carter has led these efforts since 1986, when the Carter Centre and Unicef joined the campaign.Only one human disease has ever been successfully eradicated: smallpox. As with guinea worm, there is also a continuing effort to eradicate polio, but such efforts often face their greatest obstacles in the last phase of stopping the disease.