A cholera epidemic spreading across West Africa has sickened tens of thousands of people this year and killed nearly 500 amid a long-term deterioration in health services in one of the world's poorest regions, the UN said Thursday.

Cholera has stricken 31,259 people in nine west African countries since June and 488 are reported dead in what the UN said was an "unusually high incidence" of the disease. Year-ago figures weren't provided.

"We have a crisis that needs immediate attention," said Herve Ludovic de Lys, head of the UN's humanitarian-affairs coordination efforts in the region. "This crisis needs a rapid response."

As heavy rains continue across West Africa, the disease often transmitted by infected water is likely to spread into Nigeria, Cameroon and Chad in coming months, the world body said in a statement.

The increase in cholera this year is part of a longer-term deterioration of health services in West Africa, de Lys said.

"It's a region which worsens each year. That's the reality of West Africa and the situation in which we're working," de Lys said of the region containing many of the world's least-developed nations.

Difficult climactic conditions and conflict cause mass movements of people, hurting efforts to contain the disease that causes death by dehydration from diarrhea and vomiting, said de Lys.

Cholera can be treated easily if patients are rehydrated quickly.

Cholera is often transmitted by infected water, rarely a problem in rich nations but all-too common in a region of pit latrines, untreated drinking-water supplies and communal wells.

Chlorinating wells, improving sanitation and boosting knowledge of how the disease is spread would help cut the spread of cholera, experts say.

The UN said West African countries so far reporting cholera infections and deaths are Guinea-Bissau, Liberia, Mauritania, Guinea, Senegal, Burkina Faso, Mali, Ivory Coast and Niger -- epicenter of the region's deadly food crisis.

Farther south, a cholera outbreak among soldiers and their families in eastern Congo killed at least 19 people and sickened over 700 in recent days.

The worst-hit country in West Africa, per capita, is the former Portuguese colony of Guinea-Bissau, where nearly 1 percent of the country's 1.5 million people have fallen ill with cholera.

After years of civil conflict and poor governance, the country's health care system is in shambles. Health authorities have reported 9,047 infections including 172 deaths between June 6 and August 21.

Hardest hit are residents of the crumbling capital, Bissau, where bullet holes still pock buildings and tanks lay rusting alongside roads after the country's 1998-1999 civil war.

The UN said Guinea-Bissau's situation could worsen.

"If nothing happens, we could have an unimaginable toll," said John Mulangu, a top regional official of the UN's World Health Organization.

Increased funding and health care material for treatment and prevention efforts are needed, officials said.

"It's a focal point and we need to pay attention to avert a humanitarian disaster," said Mulangu.

(Chinadaily.com.cn via agencies, September 2, 2005)