At least 135 people have died in a suspected cholera outbreak, and aid groups are rushing in medicine and other supplies today to combat Haiti's deadliest problem since its devastating earthquake.

The outbreak in the rural Artibonite region, which hosts thousands of quake refugees, appeared to confirm relief groups' fears about sanitation for homeless survivors living in tarp cities and other squalid settlements.

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"We have been afraid of this since the earthquake," said Robin Mahfood, president of Food for the Poor, which was preparing to fly in donations of antibiotics, dehydration salts and other supplies.

Many of the sick have converged on St. Nicholas hospital in the seaside city of St. Marc, where hundreds of dehydrated patients lay on blankets in a parking lot with IVs in their arms as they waited for treatment.

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.

"What we know is that people have diarrhea, and they are vomiting, and (they) can go quickly if they are not seen in time," Huck said. She said doctors were still awaiting lab results to pinpoint the disease.

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.

"The concern is that it could go from one place to another place, and it could affect more people or move from one region to another one," he said.

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 rehydration serum.

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No cholera outbreaks had been reported in Haiti for decades before the earthquake, according to the U.S. Centers for Disease Control and Prevention. Haitian officials, including President Rene Preval, have been pointing to the lack of severe disease outbreaks as a hard-to-see success of the quake response.

With more than a million people left homeless by the disaster, however, experts have warned that disease could strike in the makeshift camps with nowhere to put human waste and limited access to clean water.

At the hospital, some patients including 70-year-old Belismene Jean Baptiste said they got sick after drinking water from a public canal.

"I ran to the bathroom four times last night vomiting," Jean Baptiste said.

The sick come from across the Artibonite Valley, a starkly desolate region of rice fields and deforested mountains. The area 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.

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.

"Police have blocked the entry to the hospital, so I can't get in to see my wife," Tranckil said.

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.