The Centers for Disease Control reported Wednesday that five people have died in Mississippi and Texas due to disease contracted from the contaminated floodwaters left behind by Hurricane Katrina.

The deaths confirm health officials fears about the health risk posed by the toxic waters. With most of the hurricane victims now evacuated to emergency medical centers and shelters far from New Orleans' toxic flood, news Tuesday of four deaths from waterborne bacterial infection circulating in Katrina's flood waters proved that the waters were still a major health concern among evacuees.

But despite news Wednesday of a fifth death attributed to diseased water, a large scale break-out of infectious disease has so far not materialized, and officials said the chances of that become less likely as time goes on.

The deaths appear to have been caused by Vibrio vulnificus, a germ common in warm Gulf Coast waters that's usually spread by eating contaminated food but that can penetrate open wounds, too. The four deaths reported Tuesday — one a hurricane refugee evacuated to Texas, the other three in Mississippi — were attributed to wound infections, said Tom Skinner, spokesman for the Centers for Disease Control and Prevention, which received the reports from officials in the two states.

The reports underscore advice issued by federal health officials Tuesday: Rescue workers and anyone left in hurricane-ravaged areas should try to limit direct skin contact with flood waters; seek immediate medical attention if they have cuts or other wounds exposed to the dirty water; and wash their hands frequently.

Officials in Houston's Astrodome handed out alcohol-based hand sanitizers Tuesday to help prevent spread of norovirus, an easily spread cause of diarrhea and vomiting. Officials isolated some refugees with the illness, made infamous by recent cruise-ship outbreaks, although they couldn't provide an exact count. There is no treatment except to keep sufferers hydrated; it normally lasts a few days.

Though there are no large outbreaks yet attributed to the hurricane, infection control within shelters housing thousands of evacuees is a top priority, said Dr. Julie Gerberding, the CDC director.

Wounds infected by submersion in New Orleans floodwaters tainted with raw sewage and other bacteria are common, however. Gerberding said Tuesday that another concern is whether those waters also were contaminated with toxic chemicals from hurricane damage to nearby factories.

The Environmental Protection Agency began testing what is in the water, with the first results expected by week's end.

That's a key question for a new federal task force of medical and environmental authorities who began setting up Tuesday at Kindred Hospital in New Orleans, to monitor for disease outbreaks and "begin to make judgments about when New Orleans is safe to reinhabit," said Health and Human Services Secretary Mike Leavitt.

Drinking water safety also is an issue in much of Mississippi and Louisiana and parts of Alabama, and the EPA sent a mobile laboratory to Mississippi Tuesday to help assess that. More than 1,000 drinking water systems in the three states were affected by the hurricane.

CDC's Gerberding sought to put to rest concern about disease from exposure to dead bodies in the flooding — the corpses aren't infectious — or from agents not typically seen in this country, such as cholera.

Instead, doctors are being urged to watch for more likely causes of diarrheal illnesses: E. coli bacteria; the easy-to-spread noroviruses that, while seldom life-threatening, can cause days of misery; or Vibrio vulnificus, cholera-like bacteria that every year kill more than a dozen Gulf Coast residents. The deaths reported Tuesday were among elderly people or those with weak immune systems, CDC's Skinner said.

But infection isn't the biggest medical challenge, Gerberding said. Instead, it's how to care for thousands of people with chronic diseases like diabetes or kidney failure, many of them elderly patients who depend on numerous medications daily.

In Tupelo, Miss., for instance, city doctors brought sacks full of prescription drug samples to the Good Samaritan Clinic, where volunteer doctors are treating about 100 evacuees a day almost exclusively for chronic conditions, said Dr. J. Edward Hill, one of the volunteers and president of the American Medical Association.

For more of FOX News' coverage of the health risks posed by Hurricane Katrina, click on the video box above.

FOX News medical contributor Dr. Manny Alvarez said that the destruction wrought by the storm would continue to pose a health threat long after the water was drained. The wetness left behind creates an environment for mold and bacteria to develop, he said.

The storm also destroyed the city's medical infrastructure, Alvarez warned, leaving residents without any facilities or resources that can provide them with health care.

"All of the health care structures in New Orleans and around New Orleans are devastated," he said. "A lot of these people got their clinical care at community health centers and mental health centers. All of that is gone."

Alvarez, who spent four days volunteering at a shelter in Baton Rouge, La., said that while the focus has been on treating acute patients, the larger crisis would be with people with chronic conditions who have not had their medications.

"This will be one of the greatest American health tragedies of the century," Alvarez said.

Mental Health Crisis

While doctors and officials have been cautiously optimistic about the chances of containing, if not averting, major outbreaks of infectious disease, they continue to warn of the psychological fallout of Katrina.

Hurricane Katrina has wrenched the lives of its survivors, rescue workers and even a transfixed nation that watched the catastrophe unfold, and doctors say a widespread mental health crisis is inevitable.

Even after they reach safety physically, the survivors of Katrina have plenty of psychological pressures to cope with. They may not know the fate of family members and friends. They may not know if they have houses to return to. The social fabric of their everyday lives, things as mundane as the stores they shopped at, has been disrupted. They have little control over their lives and they've seen horrible things.

That will lead to "ordinary reactions to extraordinary events," said Gerard Jacobs, director of the Disaster Mental Health Institute at the University of South Dakota.

The symptoms include: anxiety; anger; depression; trouble concentrating; memory problems; nightmares; headaches; and withdrawal from other people and activities.

Some survivors — and it's not clear how many — could develop post-traumatic stress disorder, a long-term reaction that includes flashbacks and intrusive thoughts.

Jacobs, who expects little chronic PTSD to develop, said the other symptoms typically last for six to eight weeks after a catastrophic event ends. But he notes that it's hard to tell when an event like Katrina really ends, with the long-term disruption in people's lives.

"I think in each individual, it's going to be a question of when they see the event as being over and when they see themselves as beginning the recovery process and moving forward," Jacobs said.

The psychological toll of Katrina has already become tragically apparent. In New Orleans, a policeman, apparently distraught over his inability to rescue people, stuck a gun in his mouth and committed suicide. At least two other suicides have been reported.

At shelters like the Houston Astrodome, sleep deprived victims struggle to cope as the reality of their ordeal sets in.

"I'm depressed, I'm stressed out," said a 30-year-old mother of two who worked as a hotel chef in New Orleans. "It all happened so fast. We see this every day, homeless people living in the streets, but I didn't expect it to happen to our whole city."

"One of the biggest challenges of this is the mental health piece," Dr. Alvarez said.

People with existing mental health problems have not been receiving their medications or therapy, while the trauma of the storm has triggered depression, anxiety and trauma in others.

Although children are mentally very resilient, Alvarez said the long-term instability the hurricane has brought to many of their lives might ultimately leave psychological scars.

"In the first days, the children are in the shelters jumping, playing, entertaining themselves," Dr. Alvarez said. "But now they are seeing their parents depressed, crying. The insecurity being developed now is overwhelming and that may scar them later on."

Experts say, however, that many of the survivors will not be permanently impaired.

"I would expect to see most people recover and be fine," said psychologist Andrew Baum of the University of Pittsburgh, who studies reactions to disasters. "People do better than we expect them to."

That would be a welcome change for Selika Thomas, whose home is currently the Astrodome.

Barry Hong, a psychiatry professor at Washington University School of Medicine in St. Louis, who has studied flood survivors, said he would guess that maybe half of the survivors might need counseling or other formal psychological treatment, while the other half may do fine on their own with help from family and friends.

It will be crucial for survivors to regain a sense of normalcy and control over their lives by getting jobs and putting their kids in school and to reconnect with their families and friends, he said.

Jacobs said that in his study of survivors of the Indonesian tsunami: "It strikes me how strong the people are and how they're able to look forward. That's more the norm than the exception... I think you'll find that in the South, too."

But Dr. Irwin Redlener, director of the National Center for Disaster Preparedness at Columbia University and president of the Children's Health Fund, is not so sure that lessons of previous disasters can be applied to Katrina.

Speaking by telephone from hard-hit Biloxi, Miss., Redlener said the scope of destruction and dislocation caused by Katrina means all bets are off for assessing their psychological futures.

"I wouldn't be too quick to predict how this is going to turn out," Redlener said.

Hong agrees it is hard to tell what will happen.

"If I was going to bet, I'd bet on resilience. Most people bounce back," he said.

Rescue workers are at risk for psychological fallout too. One of the New Orleans policemen who killed himself, Sgt. Paul Accardo, was troubled because he could not help stranded women who were pleading for water and food, his boss said. He even wanted to help animals lost in the disaster. Unable to stop the unfolding catastrophe, he sank into depression.

Baum said trained rescue workers tend to be very resilient, even in the face of grotesque experiences. Hong agreed but noted that in this case, police and other rescuers also lost homes and had family members to worry about.

Chaos Hampers Care

A state-of-the-art mobile hospital from North Carolina, which had been prevented from treating patients in Louisiana because of red tape, was finally treating patients in Mississippi Tuesday.

In the first 16 hours, doctors treated about 100 people suffering from nasty head wounds, car crash victims, cuts from storm debris and dehydration.

"Mississippi stepped up and said if they don't want you, we'll take you," Dr. Thomas Blackwell, medical director of the hospital and an emergency doctor at Carolinas Medical Center in Charlotte, N.C., said Monday.

He said the delay in getting deployed was a dispute with Louisiana over what they would be allowed to do. Yet he held back criticism.

"If anybody thinks this is going to go smoothly, it doesn't work that way. This is the biggest natural disaster we've ever had," he said.

The futuristic $1.5 million emergency response hospital is getting its first real tryout since the Department of Homeland Security established it. The 113-bed hospital travels in a convoy that includes two 53-foot trailers. Equipment includes ultrasound, digital radiology, satellite Internet and a full pharmacy. It allows doctors to do most types of surgeries.

To get the hospital up and running, doctors cleared trees and other big debris by hand from the parking lot.

They needed some bolts and decided to hunt for some in the Kmart, but when they opened it, all they found were bodies inside — more evidence of the deadly storm.

One of Monday's patients was 3-year-old Brennin Wane, wearing only underpants and clutching a Santa Claus doll. He had a large leg cast over a wound that was becoming infected. Within minutes a nearby computer screen displayed an X-ray of the child's leg, taken on the spot.

George Talley, 28, evacuated his home a mile away ahead of the hurricane.

"I live down the street, or I used to. The house is off its foundation. It's in the woods next door," Talley said.

Meanwhile, the chief of the Louisiana State University public hospital system was trying Tuesday to track approximately 350 patients transferred to FEMA officials to be evacuated from New Orleans.

Don Smithburg, of the LSU Health Care Services Division, said he has heard unverified reports that patients from the system's Charity and University hospitals in New Orleans could be scattered throughout Louisiana, other nearby states and as far away as Michigan and South Carolina.

The LSU system oversees the operations of Louisiana's charity hospitals across the state. Tracking down every evacuated patient is expected to take some time.

Officials with hospitals, shelters, long-term care facilities and any other facilities that have taken patients evacuated from Charity or University hospitals in New Orleans are asked to call LSU hospital headquarters at 800 735-1185.

At the Women's Hospital in Baton Rouge, La., Dr. Steven Spedale, chief neonatologist, told FOX News that the 121 babies evacuated out of New Orleans' public hospitals were all doing well and that the parents for all but one of the babies had been found.

The rescue of the babies — some who were born 13-14 weeks prematurely — has been one of the most dramatic stories to come out of the storm. The babies stranded in the flooded University Hospital were rescued from the hospital's rooftop by helicopter.

"Every one made it okay and is doing fine," Spedale said.

The Associated Press contributed to this report.