Legions of doctors and nurses are frantically patching together a new medical care network to handle the swelling flow of Hurricane Katrina's victims. The extraordinary process includes the task of converting basketball arenas, an abandoned Kmart and even the New Orleans airport into working hospitals and clinics.

The storm -- and more significantly the flooding, lack of food and exposure to the baking sun that doctors say left victims to "rot alive" -- have presented medical workers with an overwhelming challenge. Overnight, New Orleans and surrounding communities lost 6,000 hospital beds.

The health care demands of this disaster far outstrip those of previous ones. In seven endless days and nights, doctors have delivered babies, revived failed hearts, hooked up diabetics to dialysis, bandaged snakebites and distributed thousands of medications, including many antibiotics for cases of gangrene and other infections caused by the lethal pairing of open wounds and putrid water.

"This is the worst disaster I've ever seen in my life," said Robbie Prepas, a midwife from San Diego who arrived a week ago with a federal Disaster Medical Assistance Team, or DMAT. "And I have been to disasters in Afghanistan, Asia, Africa, Guam after the typhoon."

With an influx of patients who are predominantly poor and in poor health, the emergency medical challenges are compounded by longer-term issues of managing chronic conditions such as high blood pressure, heart disease, diabetes and mental illness. At the same time, officials say they remain on the alert for outbreaks associated with flooding, such as typhoid and cholera, as well as increasing numbers of asthma attacks, fevers, rashes and suicide attempts.

Disaster care in New Orleans was far more difficult than in typical hurricane situations because of the flooding that not only forced downtown hospitals to evacuate but made it impossible for the Federal Emergency Management Agency to set up triage units in hospital parking lots, as it has done in the past.

Predictions about infectious disease outbreaks have yet to come true, though the flooding in New Orleans and disintegrating corpses throughout the Gulf Coast continue to make that a possibility. Hospitals here, operating at full capacity, have seen a spike in cases of pneumonia, stroke, lice, diarrhea and premature birth, said Louis Minsky, medical director of the Baton Rouge emergency response unit.

In many cases, people already weakened by underlying afflictions found the trauma of the storm, the days of heat and a hellacious evacuation through water, sewage and rotting garbage almost too much to endure.

"These are mostly elderly people with chronic diseases who were herded into the convention center with no medications, scared out of their minds," said Lt. Col. Constance McNabb, commander of a Texas Air National Guard unit overseeing medical evacuations in New Orleans. "I don't know how they survived."

More than 5,000 medical workers have been dispatched by the Bush administration to supplement hundreds of state, local and private health care workers. Already, the federal government has flown in 100 tons of medical supplies, including 90,000 doses of tetanus vaccine, portable oxygen tanks, gloves, sutures and antibiotics.

"Every DMAT team in this country is deployed," said FEMA spokesman Marty Bahamonde. A dozen of the 35-person teams have been treating victims in tents at Louis Armstrong International Airport, just outside New Orleans. The Centers for Disease Control and Prevention dispatched 140 people, while the Department of Health and Human Services has more than 700 people on the ground.

The unprecedented effort to provide care to tens of thousands of people has required millions of dollars, improvised medical techniques and, in at least one case, theft by a physician who persuaded local police to help him snatch medications from a pharmacy. For one full week now, doctors have worked in MASH-style surroundings, leaning over patients on flimsy military cots, flipping through textbooks to make sense of symptoms they have never seen before.

"I'm a pathologist," said Greg Henderson, a physician who moved to the New Orleans area two weeks ago. Roaming the streets of downtown in his surgical scrubs, Henderson was suddenly confronting rashes and illnesses he hadn't seen since medical school. Armed with a Physicians' Desk Reference -- the pharmaceutical bible -- and the stolen medicines, he administered to the sick and dying in a hotel lobby and the corridors of the city's convention center.

Thousands -- including infants, elderly and patients with existing health problems -- literally sat in the sun for days, with no food, water or medicine. "They basically start to rot alive," Henderson said as he led one group of ill people to McNabb's military helicopters.

Many landed on the track field of Louisiana State University here, where they were whisked into the arena named after basketball legend "Pistol Pete" Maravich. In the arena and an adjacent field house, volunteers from Illinois, New Mexico and the federal Public Health Service Commissioned Corps staffed an 800-bed hospital, making the gymnasium the largest acute care facility in the state.

"You have built a city where there was none before," Surgeon General Richard H. Carmona said after touring the improvised hospital Sunday.

With military precision, patients were designated red for most severe, yellow for serious and green for walking wounded. By Monday afternoon, 3,500 patients had passed through the arena and more than 1,400 prescriptions had been filled, said Capt. Charles McGarvey. "One night we had 800 individuals assessed by Public Health Service officers on buses," he said.

"People who were healthy enough to get up and walk out did," said James Gregory, who came to LSU with the Illinois Medical Emergency Response Team. The bulk of his patients have been diabetics, heart patients, the obese, and elderly with a full range of maladies who have no money, no home, no medications, no medical records and no doctor.

As recovery teams shifted Monday from rescuing people to retrieving the dead, health leaders here struggled to conceive of how they will provide care over the long term for hundreds of thousands of new residents.

It appears Baton Rouge has the hospital beds to serve the expected 400,000 people, said Minsky, the emergency medical director. But that amount of population growth will require as many as 2,000 more nurses and about 200 physicians, he said.

At the one-week mark, the latest challenge is treating some of the most severe cases, Minsky said. The most recent arrivals, he said, "are fatigued, been under extreme duress, prolonged exposure to the elements and inappropriate nutrition."