Dr. Jon Crocker of Partners in Health posted on the organization's Web site that people who have been lucky enough to survive their injuires so far are now falling victim to ailments such as massive infection and blood clots.
Ian Rawson, head of the Albert Schweitzer Hospital, told ABC News' senior health and medical editor Dr. Richard Besser that many of the hospital's employees who had previously been laid off came back after the earthquake to help save their family members.
It's the "biggest demand on this hospital I have ever seen," he said, crying.
It's a demand they don't seem to be able to meet. The hospital is running out of supplies and signs of that shortage are everywhere. They're out of crutches and running dangerously low on antibiotics. The only pain medication left is a small amount of Motrin.
"I wish we could get some medicine, some pain medicine and antibiotics," Rawson said. "These people are enduring horrible pain."
Dr. Emmanuel Fransoise, an orthopedic surgeon, hasn't left the hospital since Sunday night. He has already performed more than 20 surgeries and had dozens yet to go. He said he's not willing to give up.
"We are Haitian, we have hope," he said, adding that hope comes "from the inside."
The Associated Press contributed to this report.