The Dominican Republic has detected its first case of cholera, following the outbreak of the disease in neighbouring Haiti last month.
The patient is a Haitian migrant who had recently returned from his homeland, the health minister said.
The Dominican authorities had stepped up border controls and health checks to try to stop cholera from spreading from Haiti.
More than 1,000 Haitians have died of the disease.
Dominican health minister Bautista Rojas said the patient, a 32-year-old Haitian construction worker, was being treated in isolation in the eastern town of Higuey.
Like Haiti, the Dominican Republic had not had a confirmed case of cholera in more than a century until this year.
In Haiti, the government says 1,034 people have died and the disease is still spreading rapidly.
The charity Medecins Sans Frontieres (MSF) said its treatment centres in the capital, Port-au-Prince, were being overwhelmed by new patients.
“If the number of cases continues to increase at the same rate, then we are going to have to adopt some drastic measures to be able to treat people,” said MSF’s head of mission Stefano Zannini.
“I can easily see this situation deteriorating to the point where patients are lying in the street, waiting for treatment.”
The epidemic has provoked fear and anger in Haiti. The country was already struggling to recover from a devastating earthquake in January which killed about 230,000 people in and around the capital Port-au-Prince and shattered its already poor infrastructure.
On Monday two people died during violent protests against UN peacekeepers, whom some Haitians accuse of bringing cholera into Haiti.
At least one of the men was shot dead by the UN troops.
There were further clashes between youths and peacekeepers in several towns on Tuesday.
Haitian president Rene Preval has appealed for calm.
“Disorder and instability have never brought solutions to a country going through hard times,” Mr Preval said.
“Gunshots, throwing bottles, barricades of burning tyres will not help us eradicate cholera. On the contrary, it will prevent the sick from receiving care.”
President Preval also accused unnamed groups of exploiting the cholera epidemic to provoke popular unrest against the government and the UN mission, Minustah, ahead of presidential elections due on 28 November.
The UN has said there is no evidence to support allegations that cholera was brought into Haiti by peacekeepers from Nepal, where the disease in endemic.