Incidence estimates vary widely because most cases are not detected. Even when cases are detected, the public rarely hears about them, because only a small percentage occur as part of the multicase outbreaks that sometimes make the news. The disease is seldom publicized even when lawsuits are involved, because most are settled quickly and under terms of confidentiality.

A lot like pneumonia

Symptoms of Legionnaires’ are similar to those of other types of pneumonia, so undetected cases end up being classified as pneumonia with no apparent cause (“atypical” pneumonia).

Many of these deaths could be prevented because, unlike most pneumonias, the source (e.g., a cooling tower) of Legionnaires’ can be identified. But if legionella is not recognized as the cause, no investigation ensues to pinpoint and disinfect the source, so the same source remains a threat to other lives.

Cooling towers have been implicated in many outbreaks on the theory that legionellae-con-taminated water mist drifted from the tower to victims inside the building via an outdoor air intake or through windows, or directly to victims outside but near the building. Plumbing systems, a perfect habitat for legionellae, have also been implicated in numerous outbreaks.

Biofilm that coats potable water and cooling tower piping is a primary contributor to legionellae growth. Biofilm is a slimy structure that is formed as microbes attach to underwater surfaces. Biofilm and scale that form in valves and fittings and on pipe walls not only feed legionellae, but also protect them from hot water and chemical disinfectants.

As biofilm grows, fragments break off and flow into the water, releasing potentially high levels of legionellae into the system.

What to know

Here is an update on Legionnaires’ disease and legionellae control:

• Public awareness.

Last November CNN & TIME, a TV newsmagazine, aired a segment on Legionnaires’ disease in hospitals. CNN reported that “Every year, thousands of patients contract [Legionnaires’] disease from contaminated hospital water systems.” The show included an interview with Dr. Victor Yu, a Legionnaires’ expert from the VA Medical Center in Pittsburgh, PA.

“These outbreaks — they’re actually occurring all through the country every week,” said Yu. “It’s an explosive problem to realize that people are dying, to realize that the means are there for preventing all this from happening, and that those means are not being exercised.”

Indeed, more people are learning that Legionnaires’ disease is widespread, and that preventive measures are not implemented in most buildings. A new, 15-min test for a common strain of legionellae makes patient testing easy, which should result in more testing and more diagnoses.

As more cases are detected, more attention will be given to plumbing, cooling towers, and other sources of contamination.

• Outbreaks.

  The biggest outbreak of last year — and one of the biggest ever — occurred in the Netherlands in late February to early March 1999. It involved 242 cases of illness and 28 deaths. The outbreak was blamed on a whirlpool spa displayed at a trade show.

• Lawsuits.

  Legionnaires’ disease is conducive to lawsuits; several are in process at this time. A case of Legionnaires’ can be linked to an environmental source (such as a cooling tower) by comparing the legionellae strain found in the victim to the strain found in a water sample.

• Water sampling.

  The debate continues about whether or not to test water routinely for legionellae. The U.S. Centers for Disease Control and Prevention (CDC), Atlanta, GA, does not recommend sampling unless cases of disease have been identified, but some building owners voluntarily test plumbing systems and cooling towers for legionellae in order to check preventive measures and establish a defense against lawsuits.

• New disinfection technology.

  In plumbing systems, copper-silver ionization has outperformed chlorine, partly because of its apparent ability to disinfect systems laden with biofilm. Studies indicate chlorine dioxide is more effective than chlorine, lower in cost, less harmful to ingest, and less likely to cause pipe leaks. Suppliers claim it even removes biofilm over time.

  Chlorine dioxide may be effective against legionellae in cooling towers also. Chlorine dioxide has been used for years in the United Kingdom, but is still uncommon in the U.S., partly because of concerns about the safety of on-site generation.

  New technology (by Halox, Chalfont, PA) makes the generation process much safer than before, so it may soon gain acceptance here. Look for reports of studies on actual cooling towers and plumbing systems, rather than laboratory models.

  Another biocide from Sterilex (www.sterilex.com), recently accepted by the EPA, also claims to remove biofilm from cooling tower piping. The product is added to cooling towers periodically as a supplemental biocide.

• Regulations.

The New York State Department of Health (NYDOH) was to send a letter of Legionnaires’ recommendations to some 250 hospitals and 650 nursing homes early this year.

A NYDOH official said it is recommending routine sampling in hospitals that treat high-risk patients. The state of Maryland has also begun the process of drafting Legionnaires’ guidance.

Links

• HC Information Resources, Inc.