by Dehlia Ricks
September 30, 2007

The bacterial infection got its name 31 years ago, when dozens of attendees at an American Legion’s convention in Philadelphia came down with an inexplicable illness that caught experts off guard. To this day, Legionnaires’ disease is a mystery.

Scientists know without question that Legionella, the bacterium that causes the disease, is a water-loving microbe that thrives in soil and is capable of colonizing in air conditioning systems, hot water tanks and other drinking water systems. What they’ve begun to more precisely document is its ubiquity in the environment and the various ways it can be transmitted.

The recent cluster of Legionnaires’ cases on Long Island has triggered widespread testing at two residential facilities for elderly people. Results of sampling from one of those centers, Sunharbor, a nursing home in Roslyn Heights where two residents with the disease died, has traced Legionella to a cooling tower involved in the air conditioning system. The tower is not a usual hiding place for the bug, said Janet Stout, director of Special Pathogens Laboratory at the University of Pittsburgh where scientists focus on the study of Legionella.

“The majority of cases are caused by colonies in warm-water distribution systems because there is a presence of organic nutrients, what we would call biofilm,” she said.

Stout said Legionella is one of the easiest bugs to prevent in health care settings just by being vigilant. But she and her colleagues estimate that 50 percent to 70 percent of all buildings worldwide, health care institutions included, have water systems that are contaminated by Legionella.

“I always described the family of Legionella as a big one,” said Stout, who, along with her colleague, Dr. Victor Yu, a professor of medicine at the university, is calling for more rigorous testing and treatment standards, steps that can prevent unnecessary infections in hospitals and nursing homes. In all, there are 41 subtypes of Legionella, Stout said.

“One member, Legionella pneumophila, causes 90 percent of all infections, and it is the one that caused the outbreak in Philadelphia in 1976,” Stout said.

This past week, state health officials confirmed seven cases of Legionnaires’ disease on Long Island. Samples are still being evaluated from the Sunrise Assisted Living facility in Smithtown, where five residents were infected, including one who died. State and local health officials say because the residents who died were elderly and suffered from numerous medical conditions Legionnaires’ may not be the sole cause of death.

Stout said even when the source of the bacteria is found, it is not always a simple task determining exactly how people become infected.

Dr. Pascal Imperato, who chairs the department of preventive medicine at SUNY Downstate Brooklyn, said the notion that people contract Legionnaires’ through showering is one of the enduring myths about the disease.

Imperato, who was New York City’s health commissioner in 1976, was one of the experts called upon to help solve the Legionnaires’ disease mystery. He said much of what was learned about Legionella during the outbreak evolved from intense brainstorming by scientists and public health officials who wanted to quickly understand how the convention-goers were infected – and with what kind of organisms. A clue arose from a scant mention in the scientific literature of the late 1940s, which discussed a little-known bacterium with the potential to cause serious disease.

Now, experts are aware that elderly people in nursing homes can contract the organism through feeding tubes and other medical apparatus that would allow people to aspirate the microbe. Legionella is not spread person to person.

Copyright © 2007, Newsday Inc. Reprinted with permission.