New pattern for Legionnaire's Disease?

--Health officials say it's possible as many as 4,500 Americans die of Legionnaires' disease each year. They can't say for sure, because many patients don't get tested for it.

Where do some people catch Legionnaires,' and what is the government doing to stop it?

A CBS News Eye on America investigation by Wyatt Andrews turned up some surprising answers.

When 70 year old Ernest Gresko died of Legionnaires' disease three years ago, his death fit an alarming pattern.

"He was so congested he could not breathe," Valerie Greene.

Gresko was admitted to a Michigan hospital with symptoms of pneumonia, which mimic Legionnaire's--but according to his daughter Valerie Greene, he wasn't tested for Legionaires' for five days. The results came after he died.

"It was the most horrible painful death that anyone could imagine," says Greene. She faults the hospital for not testing for Legionella from moment one.

"They need to be testing their patients, that's essential," says Richard Besser, MD of the Centers for Disease Control and Prevention (CDC).

Besser says thousands of Legionnaires' cases go undetected every year. That's because only one in five hospitals follow federal guidelines to routinely test their pneumonia patients for Legionella.

"Legionnaires' disease is greatly under reported, is under recognized by clinicians, is under tested for," says Besser.

Twenty-four years after the discovery of Legionaires, it is still killing thousands of people. And ironically many of them catch it in the hospital. When four patients died last year, here, at the Harford Memorial Hospital in Maryland, officials blamed Legionnella bacteria found in the hospital's drinking water.

"What we found was that it was in our system, and we needed to irradicate it," says Lew Sperling, Harford Memorial Hospital. He says it was a great shock.

After the outbreak, a Maryland state task force recommended that all hospitals routinely test their water systems for Legionella. A call for routine tests might sound simple, but it amounted to a revolution--a revolt against the CDC, which sets safety standards for hospitals. The CDC does not think water testing will always detect Legionella.

"If you don't find legionella in your water system, there will be this false sense of security that your hospital is safe and that will lead to even less testing of patients who develop pneumonia in the hospital," says Besser.

Nonsense, says the chief of the Maryland task force, Glenn Morris, MD.

"If you test, if you know what's going on, you can keep the cases from happening," says Morris.

Morris believes the CDC approach essentially tells hospitals to wait until patients are already sick before testing the water. He says the nation will save lives if more hospitals were testing on a routine basis.

As the experts debate the best approach, Valerie Greene worries that most hospitals aren't focusing on the danger.

"This disease is very prevalent ad most people don't even know," says Greene.

She'll never know if a medical test or a water test would have saved her father. Tragically, for most victims of Legionnaires' that too fits the pattern.

©MMII CBS Worldwide Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed