The 28-year-old man, identified as Evan Muncie, was found in the wreckage of a market where he sold rice, his family told staff at a University of Miami field hospital. He suffered from extreme dehydration and malnutrition, but did not appear to have significant crushing injuries, the doctors said.
"He was emaciated. He hadn't had anything in quite some time. He had open wounds that were festering on both of his feet," said Dr. Mike Connelly of the university's Project Medishare.
The people who brought him to the hospital said they found the man while digging out the marketplace, Connelly said.
The man told doctors that someone was bringing him water while he was trapped, but doctors told CNN that he sounded confused and at times appeared to believe he was still under the rubble. Connelly said the man must have had some water during the past month to have survived, but Connelly wasn't sure how he would have had access to it.
"Initially, I'm sure he had his senses with him, so maybe he was able to find some kind of resources," Connelly told CNN.
The discovery came nearly a month after the magnitude-7.0 earthquake that devastated Port-au-Prince on Jan. 12. More than 200,000 deaths have been blamed on the quake.
Haiti's government declared search-and-rescue efforts over on Jan. 23, but survivors still were being unearthed as late as Jan. 27.
CNN's Chief Medical Correspondent Dr. Sanjay Gupta contributed to this report.
