Authorities in Haiti fear a cholera epidemic could spread to the earthquake-hit capital of Port-au-Prince.
More than 250 people have died since the outbreak began a week ago in central and northern Haiti.
At least 3,000 have been infected with the disease.
Cholera is an acute bacterial infection that rapidly dehydrates the body and causes vomiting and diarrhoea. It is spread through consumption of infected food and water. If left untreated, cholera can kill within hours.
Many of those left homeless by January’s massive earthquake still live in squalid, makeshift camps outside Port-au-Prince.
The poor sanitation and overcrowding make the ramshackle huts a fertile breeding ground for the disease.
Five cases in the capital have already been reported but UN officials have stressed they became infected after travelling in the rural north.