Health workers in central Haiti are struggling to contain the first cholera epidemic to hit the country in a century.
At least 196 people have died so far and 2,634 have been hospitalised by the illness, reports the BBC.
Aid agencies are on high alert to try to prevent cholera reaching the capital Port-au-Prince, where hundreds of thousands of people are still living in tents after January's earthquake.
The quake killed some 250,000 people and left 1.5 million homeless around Port-au-Prince.
Officials believe the outbreak in the Artibonite and Central Plateau regions was caused by people drinking infected water from the Artibonite river.
The director general of the health department, Dr Gabriel Thimote, said the worst-affected areas were Douin, Marchand Dessalines and areas around Saint-Marc, about 100km north of Port-au-Prince.
Local hospitals were "overwhelmed", and a number of people were being evacuated to clinics in other areas, he added.
Haiti is still struggling to rebuild after the devastating quake, with hundreds of thousands of people crammed into makeshift tent cities in the ruins of the capital.
Many others fled the city to live with relatives in other towns across the impoverished Caribbean nation of about nine million people, the poorest country in the Americas.
Aid agencies have voiced fears for months that any outbreak of disease could spread rapidly due to the unsanitary conditions in the camps where people have little access to clean water.
International agencies have swung into action, mobilising medical personnel to try to contain the spread of the disease and treat the sick.
Cholera is caused by a bacterium called Vibrio cholerae, transmitted through water or food that has typically been contaminated by human fecal matter.
It causes serious diarrhoea and vomiting, leading to dehydration. It is easily treatable by rehydration and antibiotics, but with a short incubation period, it can be fatal if not treated in time.