(CBS) A public health emergency has been declared in three Gulf Coast states hit by Hurricane Katrina, as officials try to prevent the outbreak of several serious diseases.

The biggest fear stems from "the combination of standing water and heat, and the conditions we're seeing with water, the unsanitary conditions," Health and Human Services Secretary Michael Leavitt said on The Early Show. "We have a recipe for disease and we want to avoid that. It would make a devastating tragedy even worse."

Leavitt told co-anchor Julie Chen the concerns are heightened because many of the hospitals are dysfunctional.

"We are rushing to develop medical shelters," he said. "We anticipate, over time, that we'll move as many as 10,000 beds into that area.

"We have 10 (shelters) … up this morning. … I will tell you that the doctors and nurses and physicians assistants and paramedics and those who are there are acting in heroic ways."

Leavitt said getting those who need medical care to facilities is a complicated problem because of the nature of their conditions and how disbursed they are.

"But, on top of that," he said, "there are common concerns that people have just because of the situation they are in.

"We are deeply concerned about the type of disease that can come from drinking water that's impure. We ask people to be working hard to educate them."

Leavitt said doctors are concerned about E. coli and, potentially, hepatitis A.

"We are also working to bring teams of public health officials into the area," he said. "Twenty-four teams of more than 20 people, a virtual army of public health officials being taken to the area. It's a big region. There are many needs.

"We are working with local and state officials, but it's of great concern to us.

The people who remain New Orleans and those who've been uncared for are the ones at highest risk, Leavitt said.

"Our heart goes out to them," he said. "We are working with every resource available to us to assure there are physicians and those who can treat them and give them the basics."