An outbreak of severe diarrhea has killed at least 135 people in rural central Haiti and sickened hundreds more who overwhelmed a crowded hospital on Thursday seeking treatment.

Health workers suspected the disease is cholera, but were awaiting tests.

Hundreds of patients lay on blankets in a parking lot outside St. Nicholas hospital in the port city of St. Marc with IVs in their arms for rehydration. As rain began to fall in the afternoon, nurses rushed to carry them inside.

Doctors were testing for cholera, typhoid and other illnesses in the Caribbean nation's deadliest outbreak since a January earthquake that killed as many as 300,000 people.

Catherine Huck, deputy country director for the U.N. Office for the Coordination of Humanitarian Affairs, said the Caribbean nation's health ministry had recorded 135 deaths and more than 1,000 infected people.

The president of the Haitian Medical Association, Claude Surena, said the cause appeared to be cholera, but added that had not been confirmed by the government.

Cholera is a waterborne bacterial infection spread through contaminated water. It causes severe diarrhea and vomiting that can lead to dehydration and death within hours. Treatment involves administering a salt and sugar-based re-hydration serum.

The sick come from across the rural Artibonite region, which did not experience significant damage in the Jan. 12 quake but has absorbed thousands of refugees from the devastated capital 45 miles (70 kilometers) south of St. Marc.

Some patients said they drank water from a public canal, while others said they bought purified water. All complained of symptoms including fever, vomiting and severe diarrhea.

Trucks loaded with medical supplies including rehydration salts were to be sent from Port-au-Prince to the hospital, said Jessica DuPlessis, an OCHA spokeswoman. Doctors at the hospital said they also needed more personnel to handle the flood of patients.

Elyneth Tranckil was among dozens of relatives standing outside the hospital gate as new patients arrived near death.

Aid groups were mobilizing to ship medicine, water filtration units and
other relief supplies to the Artibonite region.

The U.S. Embassy in Port-au-Prince issued an advisory urging people to drink only bottled or boiled water and eat only food that has been thoroughly cooked.