Legionella bacteria on the rise, but difficult to find and destroy

Legionella, the shifty bacterium that causes Legionnaires' disease, is tough to find and even tougher to destroy once it colonizes inside hotel, nursing homes or hospital plumbing systems.

It can remain dormant for years, waiting for a dip in disinfectants or ideal water temperatures to emerge and infect people with an aggressive form of pneumonia. The water-borne bacterium thrives in biofilm (slime) and is best transmitted in the aerosol mists of showers and hot tubs.

Standards and strategies to eradicate Legionella are lacking, with evidence that infections continue to rise nationwide.

The U.S. Centers for Disease Control and Prevention cites an incidence rate of more than 1 case per 100,000 in the U.S. -- more than double the rate of 10 years ago, with the incidence rising annually.

The elusive characteristics of Legionella were tragically apparent in the 2011-12 outbreak in the Veterans Affairs Pittsburgh Healthcare System, with up to six deaths and 16 veterans infected.

Identifying, reporting and resolving the outbreak has become the goal of congressional hearings and federal bills to require veterans hospitals -- as required of other hospitals -- to report infections to local, state and federal health departments.

Ali Sonel, chief of staff for VA Pittsburgh, said the strain of Legionella that caused the outbreak was the same strain that caused an outbreak in the 1980s. VA hospital officials found the strain in a remote area of plumbing but thought it too distant to cause the recent outbreak. Further investigation revealed it to be the source of the infections.

"What we have in the facility is Legionella that never entirely goes away," Sonel said.

Legionella concentrations form in stagnant water or dead-end areas of plumbing. While the focal concern is public buildings, due to the potential for major outbreaks, Legionella can exist in any plumbing system, including homes. The bacterium thrives in water temperatures of 77 to 108 degrees Fahrenheit.

Along with shock chlorination, a heat-and-flush method can be used to get rid of Legionella; water is heated to 140 degrees before being flushed through the plumbing, with the goal of maintaining at least 124 degrees as it courses throughout water pipes. Other methods involve the use of monochlorination, chlorine dioxide and copper and silver ionization. Officials agree that each method has advantages and disadvantages, but none is guaranteed to work.

Legionnaires' disease and the bacterium got their names from the 1976 outbreak in which 221 cases resulted from an American Legion Convention in Philadelphia, with 34 deaths. The source of Legionella eventually was traced to the hotel's rooftop water cooling tank.

Neither state nor national standards exist for plumbing systems. Guidelines for analyzing systems to monitor Legionella levels in heating and cooling systems are in the works.


(Contact Pittsburgh Post-Gazette writer David Templeton at dtempleton@post-gazette.com. Distributed by Scripps Howard News Service, www.shns.com.)

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