The Dominican government bolstered patrols along the 130-mile-long border to halt the entry of undocumented foreigners infected with the disease, which has killed as many as 300 Haitians.
It follows UN peacekeepers firing tear gas to disperse a crowd awaiting to cross into the northwestern town of Dajabon.
President Leonel Fernandez announced the decision after meeting with the ministers of the armed forces and public health.
The only Haitians who will be allowed to enter the country are those who take part in the cross-border markets. These Haitians use designated bridges.
The outbreak that already has left more than 300 people dead and thousands more ill at the doorstep of an enormous potential breeding ground: the squalid camps in Port-au-Prince where 1.3 million Haiti earthquake survivors live.
Health authorities and aid workers are scrambling to keep the tragedies from merging and the deaths from multiplying.
Five cholera patients were reported in the capital, Port-au-Prince, heightening worries that the disease could reach the sprawling tent slums where abysmal hygiene, poor sanitation, and widespread poverty could rapidly spread it.
But government officials said all five apparently got cholera outside Port-au-Prince, and they voiced hope that the deadly bacterial disease could be confined to the rural areas where the outbreak originated last week.
'It’s not difficult to prevent the spread to Port-au-Prince. We can prevent it,' said Health Ministry director Gabriel Timothee.
He said tightly limiting movement of patients and careful disposal of bodies can stave off a major medical disaster.
If efforts to keep cholera out of the camps fail, 'The worst case would be that we have hundreds of thousands of people getting sick at the same time,' said Claude Surena, president of the Haiti Medical Association.
Cholera can cause vomiting and diarrhoea so severe it can kill from dehydration in hours.
Robyn Fieser, a spokeswoman for Catholic Relief Services, said she was confident that aid groups and the Haitian government will be prepared to respond to an outbreak should it occur in the camps.
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