Officials in Haiti are hopeful that a cholera outbreak is now stabilising after they confirmed that the disease has killed more than 250 people.

"We have registered a diminishing in numbers of deaths and of hospitalised people in the most critical areas... The tendency is that it is stabilizing, without being able to say that we have reached a peak," Gabriel Thimote, director-general of Haiti's Health Department, told a news conference.

Thimote said that whereas previously the hospital in Saint-Marc in the Artibonite region was recording deaths by dozens, it had registered only one on Saturday.

The epidemic is the second emergency to strike the poorest country in the Western Hemisphere this year. A catastrophic quake killed up to 300,000 people in January.

Despite the reports of a stabilizing trend in the cholera outbreak, foreign aid agencies were preparing for a possible worst-case scenario of the epidemic spreading across the country, including the densely populated capital.

The detection of five "imported" cases in Port-au-Prince, involving patients who had travelled south to the city from the central outbreak zone, has raised fears of the virulent diarrheal disease spreading in the capital.

Experts see Port-au-Prince's sprawling, squalid slums and tent and tarpaulin camps housing some 1.3 million homeless quake survivors as vulnerable to the cholera, which is transmitted through contaminated water and food.

If left untreated, cholera can kill in hours by dehydrating victims with severe diarrhoea, but if caught early it can easily be treated by an oral rehydration solution, or a simple mixture of water, sugar and salt.