In the aftermath of Hurricane Katrina, those affected have had to deal with many challenges, and now there is another growing concern -- disease. 

Floodwaters from Hurricane Katrina cover a large portion of New Orleans

Thousands of displaced people in New Orleans, still without food or water...  Survivors making their way past corpses left on the street ... 

"We want help!  We want help," they chant.

And the floodwaters that submerged approximately 80 percent of the city of New Orleans have now become a dangerous sea of gasoline, sewage, decay... and a breeding ground for disease.

Dr. Julie Gerberding of the Centers for Disease Control warns, "The infectious diseases would be those associated with sewage and so any of the infections that are associated with diarrheal illness could be in the water."

The CDC is trying to prevent the spread of some diseases.

Julie Gerberding, CDC  (file)

"We have more than 30 people deployed to Mississippi and Louisiana.  We have a plane in the air right now flying vaccine to Jackson, Mississippi."

Besides the broken sewage systems, the drinking water systems have been breached and are no longer functioning.  It's an enormous problem requiring immediate attention, yet officials cannot even predict how long it will take before they can provide safe, drinkable water.

As displaced people fall ill, they have nowhere to go for treatment.  Area hospitals have either been evacuated, or are filled to capacity.  They are running on battery power only, and their batteries are running low.

Speaking by phone, Elizabeth Rees, a nurse at Charity Hospital in New Orleans, says the situation there is critical for people on respirators.

"Most of these ventilators are being run by batteries and when we don't have batteries -- unfortunately, they're going to die when we have no batteries."

Part of Louis Armstrong International Airport in Kenner, Texas has been converted into a makeshift hospital.  Doctors and nurses from across the country have converged there to treat the wounded and sick from southeast Louisiana.

Some victims from New Orleans are already showing signs of flood-related illness.

"I just attended to a woman yesterday who said she was lying in water for a day and a half,” said  a medical professional. “And her back was scaly and itchy and she was having problems with skin rashes and that's because of the water, it's contaminated with sewage."

Slowly, assistance is arriving. In Hancock County, Mississippi, National Guardsmen are handing out water, ice, and ready-to-eat meals to those who can make it to the distribution center.