A cholera outbreak in southern Sudan has killed 127 people among 5,634 cases in the past month and the water-borne disease is spreading, the World Health Organization (WHO) said on Monday.

In a statement received in Nairobi, the UN health agency said all reported cases are concentrated in the town of Yei, which borders Uganda, and the vast region's main city of Juba of southern Sudan.

WHO said the two towns have been hit hardest by the epidemic, which has been spreading to surrounding areas.

"The Sudanese health authorities in collaboration with WHO and other partners reported a total number of 5,634 cases and 127 deaths from acute watery diarrhea in southern Sudan," WHO said in a statement.

Cholera, an acute intestinal infection spread by contaminated water or food, causes vomiting and acute diarrhoea that can lead to dehydration and death within 24 hours.

It is a highly contagious and potentially fatal disease that thrives in places with poor hygiene and inadequate water supplies.

It is generally caused by using dirty water for drinking and cooking.

WHO and other aid agencies are helping Sudanese authorities by providing antibiotics and chlorination tablets.

"Control measures being implemented include strengthening the surveillance and reporting system, standardizing case management and promoting health education and hygiene, with the chlorination of public water supplies," the statement said.

The UN agencies have mounted a broad effort in Yei to enhance access to clean water and sanitation as well as launch public awareness campaigns about the importance of good hygiene and clean water which include house-to-house visits, it said.

The population of Southern Sudan's towns is swelling due to the return of displaced people and refugees, and increased economic activity.

Southern Sudan remains largely underdeveloped after 21 years of civil war between the former rebels of the southern Sudan People's Liberation Movement/Army and the Khartoum-based government.

The war, which ended with the signing of a peace deal in January 2005, killed at least two million people, uprooted four million more and forced some 550,000 to flee to neighboring countries.

(Xinhua News Agency March 7, 2006)