Engulfed by putrid floodwaters that are expected to linger for weeks, New Orleans is in the grip of a public health emergency that medical experts fear may grow even more dire.

The stagnant water covering 80 percent of the city is contaminated with human and animal corpses, human waste and raw sewage, posing the potential for outbreaks of typhoid, cholera and tuberculosis.

Sewers cannot operate until the floodwaters are pumped out of the city. Since that is weeks or even months away, the stagnant water will likely become more contaminated, increasing the threat of mosquito-borne diseases like West Nile virus, dengue fever and malaria.

"These are highly contagious diseases, and as people begin to experience the diarrhea and vomiting it'll spread because we have people in very close quarters now in the Astrodome or wherever they are,” said FOX News medical analyst Dr. Steven Garner.

“Coming into contact with someone with dysentery can easily spread the disease and have an epidemic," he said.

Whatever infections people carry go into sewage and can be expected to show up in floodwaters. That includes common diarrheal germs including hepatitis A and Norwalk virus.

"You can think of floodwaters as diluted sewage," said Mark Sobsey, professor of environmental microbiology at the University of North Carolina.

"We are gravely concerned about the potential for cholera, typhoid and dehydrating diseases that could come as a result of the stagnant water and the conditions," said Department of Health & Human Services Secretary Mike Leavitt.

But officials at the federal Centers for Disease Control and Prevention and other health experts said cholera and typhoid are not considered to be high risks in the area. And some experts said worries about catching illnesses from being near human or animal corpses are somewhat overblown.

"People who are alive can give you a whole lot more diseases than people who are dead," said Richard Garfield, a Columbia University professor of international clinical nursing who helped coordinate medical care in Indonesia after the tsunami.

There are other water contaminants: Natural gas lines, propane tanks and gas station pumps damaged in the storm are leaking into the water and, in some cases, have caught fire. Overall, the water is so toxic and dangerous that health experts warn that even coming into contact with it could lead to serious health problems. But for many of the survivors who were trapped in their homes, the only route to dry land and relief is through the water.

The disease threat posed by the water is not the only health crisis unfolding in the region. Drinking water is all but non-existent in the city, and many of the survivors still making their way to shelters and relief efforts Wednesday and Thursday had not had food or water in more than two days.

Reporting from New Orleans Thursday, Fox News' Shepard Smith said rescue squads still hadn't reached thousands of victims, and many were desperate for drinking water and food. Along the freeways, refugees who had reached dry land wandered weak and aimless without water or food. An elderly man lay dead by the side of the road. On Wednesday, a group of 14 people, including a 5-day-old baby, told Smith they had spent two days trapped in the attic of a house flooded with 14 feet of water. Smith said the breakdown in communication equipment was exacerbating the problem: Without working phones, cell phones or television, survivors had no information about where to go or how to get help, and officials were not reaching the refugees on the freeways. Trapped in sweltering heat, survivors begged for help and information.

There are also the injured who need medical attention, the sick and infirm who cannot get vital medical treatments such as chemotherapy and dialysis, or who cannot get their medication for conditions like diabetes and heart disease.

Officials also cited carbon monoxide poisoning risks to people using generators and stoves.

Declaring the Gulf Coast a public health emergency, the federal government promised 40 medical centers with up to 10,000 beds and thousands of doctors and nurses for the hurricane-ravaged area. Patients requiring treatment beyond what the medical shelters can provide will be transported to hospitals out of the immediate area.

"We've identified 2,600 beds in hospitals in the 12-state area. In addition to that, we've identified 40,000 beds nationwide, should they be needed," Leavitt said.

Crippled Hospitals

Officials were trying to evacuate 10,000 people — patients, staff and refugees — out of nine hospitals battling floodwaters or using generators running low on fuel. Yet even as they tried to evacuate, many hospitals faced an onslaught of new patients — people with injuries and infections caused by the storm, people plucked from rooftops who are dehydrated, dialysis and cancer patients in need of their regular chemotherapy or radiation treatments.

"We have thousands of people who are getting ill ... our hospitals need to be prepared to take care of the incoming sick," said Coletta Barrett of the Louisiana Hospital Association.

Thursday morning, doctors at two desperately crippled hospitals in New Orleans called The Associated Press pleading for rescue, saying they were nearly out of food and power and had been forced to move patients to higher floors to escape looters.

"We have been trying to call the mayor's office, we have been trying to call the governor's office ... we have tried to use any inside pressure we can. We are turning to you. Please help us," said Dr. Norman McSwain, chief of trauma surgery at Charity Hospital.

Charity is across the street from Tulane University Medical Center, a private facility that has almost completed evacuating more than 1,000 patients and family members, he said.

No such public resources are available for Charity, which has about 250 patients, or University Hospital several blocks away, which has about 110 patients.

"We need coordinated help from the government," McSwain said.

He described horrific conditions.

"There is no food in Charity Hospital. They're eating fruit bowl punch and that's all they've got to eat. There's minimal water," McSwain said.

"Most of their power is out. Much of the hospital is dark. The ICU (intensive care unit) is on the 12th floor, so the physicians and nurses are having to walk up floors to see the patients."

Dr. Lee Hamm, chairman of medicine at Tulane University, said he took a canoe from there to the two public hospitals, where he also works, to check conditions.

"The physicians and nurses are doing an incredible job, but there are patients laying on stretchers on the floor, the halls were dark, the stairwells are dark. Of course, there's no elevators. There's no communication with the outside world," he said.

"We're afraid that somehow these two hospitals have been left off ... that somehow somebody has either forgotten it or ignored it or something, because there is no evidence anything is being done."

Hamm said there was relief Wednesday as word traveled throughout University Hospital that the National Guard was coming to evacuate them, but the rescue never materialized.

"You can imagine how demoralizing that was," he said.

Throughout the entire city, the death, destruction and depravity deepened even as the hurricane waters leveled off.

"Hospitals are trying to evacuate," said Coast Guard Lt. Cmdr. Cheri Ben-Iesan, spokesman at the city emergency operations center. "At every one of them, there are reports that as the helicopters come in people are shooting at them. There are people just taking pot shots at police and at helicopters, telling them, 'You better come get my family."'

Richard Zuschlag, president of Acadian Ambulance Service Inc., described the chaos at a suburban hospital.

"We tried to airlift supplies into Kenner Memorial Hospital late last evening and were confronted by an unruly crowd with guns, and the pilots refused to land," he said.

"My medics were crying, screaming for help. When we tried to land at Kenner, my pilots got scared because 100 people were on the helipad and some of them had guns. He was frightened and would not land."

Zuschlag said 65 patients brought to the roof of another city hospital, Touro Infirmary, for evacuation Wednesday night spent the night there. The hospital's generator and backup generator had failed, and doctors decided it was safer to keep everyone on the roof than carry fragile patients back downstairs.

"The hospital was so hot that with no rain or anything, they were better off in the fresh air on the roof," he said.

When patients have been evacuated, where to take them becomes the next big decision.

"They're having to make strategic decisions about where to send people literally in midair," said John Matessino, president of the Louisiana Hospital Association. "It's a very difficult thing to prioritize when they're all a priority."

Knox Andress, an emergency nurse who is regional coordinator for a federal emergency preparedness grant covering the state, said it's impossible to underestimate the critical role hospitals are playing for anyone left in the city.

"They're running out of their medications, they're running out of money. They're having social issues and where do they go? They go to the hospital. The hospital is the backbone of the community because the lights are always on," he said.

When hospitals can't take care of people and the rescuers need rescued, there's no social fabric left, Andress said.

In a stunning example of how desperate the situation has become, 25 babies who had been in a makeshift neonatal intensive care unit at New Orleans' Ochsner Clinic were airlifted Wednesday to hospitals in Houston, Baton Rouge, La., and Birmingham, Ala. Many were hooked up to battery-operated breathing machines keeping them alive.

Their parents had been forced to evacuate and leave the infants behind; by late in the day, most if not all had been contacted and told where their babies were being taken, said hospital spokeswoman Katherine Voss.

"We actually encouraged them to leave. It would just be more people to evacuate if there was a problem," said Dr. Vince Adolph, a pediatric surgeon.

Helicopters had to land on the roof of the parking garage to get the babies because water covered the helipad at the hospital

The government said dozens of medical disaster teams from nearby states were moving into hard-hit areas.

Leavitt said a team of mental health experts are being sent to address what could be a severe public mental health crisis brought about by grief, emmotional trauma, loss and stress.

The U.S. Navy hospital ship USNS Comfort, currently in Maryland, will be arriving in the Gulf of Mexico Sept. 8.

"One of the things they have got to do — we've got to plead for — is to make sure that when these hospitals get evacuated, the National Guard or somebody is there putting major security around these hospitals, or they're going to get ransacked. And it's going to make a bad situation even worse," said John Matessino, president of the Louisiana Hospital Association.

He said the four hospitals in New Orleans' central business district — Tulane, Charity, University and the VA hospital — had the worst problem with would-be looters.

Hospitals weren't the only facilities with troubles.

Louisiana Lt. Gov. Mitch Landrieu, who has been working with search and rescue, confirmed that 30 people died at a nursing home in St. Bernard Parish and 30 others were being evacuated. He did not give any further details.

Many people in key positions to help were still struggling to figure out how.

The Pharmamaceutical Research and Manufacturers Association asked the government to make a public health assessment to guide drug companies.

"Once we know what is required, we can begin to donate and ship in desperately needed medicines," said a statement from Billy Tauzin, the group's president and former congressman from Louisiana.

The American Diabetes Association wants to help get insulin and syringes to diabetics and is working with the Red Cross, but the relief agency "is still very much in 'rescue mode,"' an association spokeswoman said.

Eli Lilly and Co. said it would give $1 million in cash and would match any donations by its U.S. employees to the Red Cross. The company also is donating $1 million in insulin.

The American Medical Association's Center for Public Health Preparedness and Disaster Response was trying to figure out a system to help coordinate doctors who want to volunteer.

"It's going to take years — years — to rebuild the medical infrastructure. There will be continuing health needs," said Dr. James J. James, the center's director.

Click in the video box above for more coverage of the hurricane health crisis in New Orleans.

Fox News' Todd Connor, Shepard Smith and the Associated Press contributed to this report.