Though a large-scale break out of infectious disease has yet to materialize on the Gulf Coast, health experts warned Friday that a public health crisis may have yet to be avoided.

In areas where the water has receded, health officials were concerned about toxic dust the water has left behind. Reporting from Mississippi Friday, FOX News' Shepard Smith said that just about everything that had once been submerged in the polluted flood waters was now covered in a thick layer of dusty residue that may contain the same bacteria and toxins that had contaminated the water.

"We have to be very concerned," said FOX News medical contributor Dr. Manny Alvarez, volunteering at a medical shelter in Baton Rouge, La. "We're now in the recovery and cleaning phase, and we still have the potential for infection," he said.

Predicting a "mold epidemic" once the water was pumped out, Alvarez said the mold would pose serious dangers for people with asthma and allergies and said it would be weeks, if not months, before "any habitation could occur."

"You have to keep children away, you have to keep pets away," he said.

Alvarez said flood victims should be very cautious about hanging on to objects, like children's stuffed animals, rugs and mattresses, that got wet in the flood, and advised throwing out anything that could have absorbed moisture.

Meanwhile, the toxic standing flood water in New Orleans remains a threat for the rescue workers and remaining residents who come in contact with it. Dr. Alvarez said that the mold, the lack of a functioning medical establishment, and unsanitary conditions pose serious health risks even for those residents who are on dry land and have food and drinking water.

"People need to [evacuate] because their lives are in danger. There are no medical resources for them," he said.

For more on the Gulf Coast public health crisis, click on the Video box above.

Public Health Crisis in Mississippi

As a handful of businesses opened in Mississippi for the first time since the hurricane hit, Gov. Haley Barbour (search) said that the focus in Mississippi was rebuilding and recovering and less on a public health threat that he said was not a major concern in his state.

However, four people have died from waterborne illnesses at shelters in Mississippi, and while attention remains fixed on the medical emergency in New Orleans, clogged roads and communication breakdowns in some parts of devastated Mississippi have cut residents off from hospitals, the Red Cross and dire health warnings.

In Waveland, Miss., a coastal fishing village that was all but wiped off the map by Katrina, the Mississippi National Guard erected a tent hospital Friday to provide health care to an area where medical care has been non-existent since the hurricane hit, FOX News Laura Engle reported Friday.

Waveland's hospital, Hancock Medical Center, was destroyed by the storm, and the town remains without running water or electricity. The military tent hospital contains a pharmacy, a lab, a surgical unit and an emergency center, and can hold up to 25 overnight patients.

In a neighborhood called Point Cadet at the east end of Biloxi that has no clean running water, residents complain of a foul stench pervading the air, one that burns their throats and that they are sure, they say, is the smell of human decay.

In the few homes still standing, people are living in dangerously unsanitary conditions.

"This is a public health nightmare," said Dr. Mary Wells, a pediatrician from Mobile, Ala., who used her day off to drive Biloxi's debris-strewn streets to see what people need.

She found squalor and desperation. She saw people who can't get medicine, who are drinking contaminated water, who have untreated cuts and bruises from a night battling Hurricane Katrina, who don't have badly needed insulin.

Bottled water and donated food have reached churches and the neighborhood handout points. But doctors and emergency aid workers have gone unseen, let alone the critical public health warnings that could help save residents from dangerous diseases.

"We've got a first aid station in the church, but not to where we're practicing medicine," said Jill Leggett, volunteering to hand out water at the Lighthouse Apostolic Holiness Church. "If the (conditions) here are going to affect people, they need to tell people or get them out of here."

Medical officials and political leaders are worrying that the word — and the medicine — aren't spreading. Democratic Rep. Gene Taylor has urged FEMA to send 150,000 doses of tetanus vaccine to the coast now.

Federal public health teams are stationed at various points around the Gulf Coast, but are typically set up at hospitals or central locations — not deep in the areas where conditions are worst. These days the residents of Point Cadet have little or no transportation. The lack of phone service and electricity — no TV and only car or battery-powered radio — has kept them cut off from news.

Just west of Biloxi, three people died when they had wounds infected with Vibrio vulnificus, a bacterium that lives in warm salt water.

Last week a shelter in Biloxi was shut down after more than 20 residents came down with dysentery-like symptoms, and officials are also starting to get scattered reports of another stomach virus, known as norovirus, in places where large numbers of evacuees are staying.

Luckily, the fetid conditions haven't led to large outbreaks of the diseases nearly every doctor expects: illnesses caused by contaminated water, bad hygiene and people with weak immune systems.

"I think that what we have to this point is a good news story about communicable disease outbreaks," said Dr. Mills McNeill, Mississippi's state epidemiologist. "Fortunately, we are not seeing major outbreaks of illnesses. To me, that's a blessing."

But there are other potential health-related problems — one of the biggest being people who haven't been able to take their regular medications.

Carrie Jackson escaped to the roof of her Point Cadet home and since hasn't been able to take medicine for her lupus or her high blood pressure because she can't get any.

"So far, no problems," she said. Jackson said residents in her neighborhood have had no visits from health officials warning about unsanitary tap water.

"We're not getting sick, but everybody is getting a ... rash," says Janyne Evan, slogging through the mud in rubber boots as she tries to throw out rotting food at her now-ruined Turtle Landing restaurant on Cowan Bayou in Pearlington, west of Biloxi on the Louisiana line.

Like others here who've learned about the disease threat, she's been washing her hands in a bleach solution. As a restaurateur she's better versed in hygiene than some others.

On a recent day, she went looking for a Red Cross station in town but found none. Then she drove to Bay St. Louis, more than 20 miles away. Still, she couldn't find one. So more than a week after the storm, she still relies on bleach and tiny packets of antibiotic cream that the ambulance crew left.

Evan said she saw people swimming in the reeking, polluted East Pearl River, which serves as the state's southwestern border with Louisiana.

Sgt. Chuck Strain, who patrols the river for Louisiana's Department of Wildlife and Fisheries, wrinkles his nose at the thought, pointing to a blob of fur in the water. It is, he says, a roughly 10-pound nutria rat.

"There's millions of them dead out there," he said. "They're floating around with their little legs sticking up in the air and their little yellow teeth showing."

Sgt. Grady Brecheen said two of his agents have been hospitalized with dysentery. Both were in the flood waters in New Orleans.

"I think it's going to get bad," he said. "I really do."

Medical Help Needed

Dr. Alvarez said the medical shelters treating hurricane victims were still in need of volunteer doctors and nurses, especially mental health professionals. Health care experts have been concerned about a mental health crisis among refugees, both those who have been traumatized by the ordeal they have suffered, and those with existing mental health problems who have not been able to get their necessary medication and therapy.

A mental health clinic has now been established at the Baton Rouge shelter, Alvarez said.

"There alot of people here who need therapy," he said.

The Associated Press contributed to this report.