By Judy Angelbeck, Ph.D.

For many people the word Legionella conjures up memories of the Hotel Bellevue in Philadelphia, Pa. in 1976. That is where Legionnaires’ disease was first identified and named when a group of American Legion conventioneers were taken sick, some fatally, from a contaminated air conditioning system. What most people don’t realize is that the source of Legionella infection is waterborne. Legionella bacteria are one of many pathogens that are ubiquitous in the environment and occur naturally in the water supply. For the majority of people exposed to Legionella bacteria, the outcome is benign. However, for sensitive populations, such as newborns and the elderly, the immunocompromised or those recovering from recent surgery, cancer, burns, or suffering from chronic lung disease, the outcome can be serious and life threatening. The problems and risks associated with waterborne pathogens, including but not limited to Legionella bacteria, are most critical in places where there is a concentration of immunocompromised people such as in hospitals, nursing homes and long term care facilities. (See Table 1).

Hospital acquired infections increasing worldwide
Nosocomial, or hospital acquired infections, are increasing at an alarming rate worldwide. According to the U.S. Centers for Disease Control and Prevention (CDC), nearly two million patients contract infections during their stay in U.S. hospitals (about 10 percent of all hospitalized patients), resulting in significant morbidity, mortality and financial burden. In 1995, nosocomial infections resulted in 88,000 deaths in the U.S. at a cost of $4.5 billion. Simply put, hospital acquired infections affect one in 20 patients and kill more people annually than homicides and car accidents combined. The CDC also reports that 23 percent of all Legionnaires’ disease reported in the U.S. in the 1980s was acquired in hospitals and of these cases, 40 percent of the patients died, twice the rate for infections acquired outside the hospital.

Although water is often overlooked as the source of the outbreaks, it is increasingly being recognized as a significant culprit. A recent survey found that as many as five out of six hospitals in one geographic area of the U.S. had Legionella bacteria in the water supply. According to Janet Stout, Ph.D., microbiologist and Director of Special Pathogens Laboratory at the Veteran Affairs Pittsburgh Healthcare System, approximately 18,000 cases of Legionnaires’ disease occur annually in the U.S. and 25 percent of these are acquired from hospital water systems.

Despite the growing incidence, the number of outbreaks continues to be underestimated, due to mis-diagnosis and underreporting. Legionella bacteria are not automatically or routinely cultured for when a hospitalized patient contracts pneumonia. Some experts contend that hospitals may also refrain from reporting cases due to misunderstandings surrounding Legionella and the specter of negative publicity associated with it.

The incidence of hospital acquired waterborne illness has also increased throughout Europe. The European Working Group for Legionella Infections (EWGLI), which conducts surveillance in 33 countries, reports a 74 percent increase in Legionella cases over the decade, from 1,242 cases in 1993 to 4,696 cases in 2002. Although some of the increase can be partially due to better detection and improved surveillance, most experts contend that just like in the U.S, the number of cases of waterborne pathogen outbreaks in hospitals is underestimated. According to Dr. Tom Makin, Directorate Manager of the Department of Medical Microbiology of the Royal Liverpool and Broadgreen University Hospitals, extrapolation of data from a prospective study on community acquired cases of pneumonia indicates that approximately 95 percent of cases of Legionnaires’ disease are misdiagnosed or go underreported. He attributes this to the fact that the symptoms of this atypical form of pneumonia are diverse and do not assist in the diagnosis. He says that the data suggest that the current level of reported cases of hospital acquired Legionnaires’ disease is also far from accurate, perhaps by a factor of ten or more, and is also increasing. His assessment is borne out by recent cases in several UK hospitals as well as the finding that up to 70 percent of UK hospitals have Legionella bacteria in their water supply.

Biofilm and aerosolization: not just Legionella
Legionella bacteria are not the only waterborne pathogens that can put immunocompromised people at risk. There are a host of bacteria and mycobacteria as well as fungi that can also be life threatening.

An estimated 1,400 deaths occur each year in the U.S. as a result of nosocomial pneumonias caused by the waterborne bacteria Pseudomonas aeruginosa alone. This bacterium causes approximately 15 percent of all hospital acquired infections and 25 percent of all infections in the intensive care unit.

The incidence of hospital mold infections also continues to increase despite the use of high efficiency air filtration systems. This has led to recognition that water systems in hospitals can also be colonized with pathogenic molds. Studies conducted by Anaissie, found that opportunistic molds, such as the fungi Aspergillus, can become part of a water system’s biofilm and lead to patient exposure from spore aerosolization in patient care areas. (See Figure 1).

In aqueous environments, microorganisms preferentially colonize surfaces to increase their chances of survival. The colonies are part of a biofilm, communities of microorganisms adhering to environmental surfaces surrounded by the slime they secrete. These biofilms can build up on the surfaces of a facility’s water system and be found in pipes, faucets, showerheads and storage tanks.

Drinking contaminated water is one means of exposure. Exposure also occurs by breathing in the aerosols, the tiny invisible droplets of water that contain the microorganisms, which form when water hits the biofilm on the hard surface of the faucet, showerhead or pipes (See Figure 2).

Legionella and other microorganisms can be found even in hospital water systems that are well maintained. While a number of methods exist for systemic treatment that may minimize the Legionella population in the water distribution system, re-colonization frequently occurs within a few months. Legionella can resist chemical and physical disinfection schemes by living in biofilms and inside amoeba, which act as a Trojan horse and protect the bacteria. It is becoming increasingly recognized that the best approach to minimize patient exposure, particularly for high-risk patients, may be combining multiple methods, such as a systemic method with point-of-use (POU) sterilizing grade filtration.

Europe on the vanguard of prevention: POU filtration
The European community is in the forefront in acknowledging the risks of waterborne pathogens for immunecom-promised patients and is working to both identify and prevent the problem. Some nations have issued guidelines and recommendations to prevent exposing high-risk patients in the hospital environment to these pathogens.

Last year, the French Ministry of Health issued a guideline that all hospitals install a 0.2-micron filter in water units where immuno-compromised patients are treated to protect against the spread of Legionella pneumophilia. This year, an official recommendation in the Bundesgesundheistblatt, the official organ of the Robert Koch Institute of the German Health Authority, called for point-of-use filtration in hospitals especially in areas with immunocomprom-ised patients, such as hematology/oncology wards and intensive care units, in order to protect them from Legionella and Pseudomonas infections.

It has become generally accepted that 0.2 micron filters represent the most effective barrier to bacteria transmission. The CDC has identified, as an alternative to sterile water, 0.2 micron filtered water to meet the standard of the highest quality of water that is practical for final rinse of endoscopes and other medical devices. However, not all POU 0.2 micron filters are alike despite claims to the contrary. Confidence in their use should be based upon performance claims in actual clinical experience.

0.2 micron point-of-use water filters are being used with success throughout Europe. Studies conducted in transplant units, hematology/oncology units and intensive care units have shown a reduction in Legionella and Pseudomonas outbreaks and the rate of infections significantly reduced or eliminated. A new study just completed in the U.S. by the VA Pittsburgh Healthcare System found that the 0.2 micron completely eliminated Legionella pneumophilia and Mycobacterium spp and achieved a greater than 99 percent reduction in heterotrophic bacteria in the water samples (See Figure 3).

The American approach
Although it has been known and documented since 1982 that water, especially in hospitals with complex hot water systems, is the most important source of Legionella transmission, the issue of nosocomial waterborne infections is just starting to appear on the radar screen. A convergence of multiple events is planting the seeds for change. There have been an increasing number of outbreaks of waterborne infections in hospitals across the United States. We are now learning from the Europeans the value of taking more proactive measures with point-of-use filtration to prevent exposure and protect patients. The Joint Commission on Accreditation of Health-care Organizations (JCAHO) has announced implementation of a requirement for reporting of hospital acquired infections starting July 2005. The CDC recently amended their guidelines to stipulate that water in areas housing transplant patients should not contain any Legionella bacteria. The Consumers Union is conducting a Stop Hospital Infection campaign to raise awareness of nosocomial infections and support legislative efforts. Five states—Florida, Missouri, California Pennsylvania and Illinois—are in various stages of the legislative process calling for hospitals to alert the public to their infection rates.

A great deal of education is still required. As physicians, infection control professionals, hospital and nursing home administrators, patients and the public at large continue to become more educated there will be a shift from a reactive to a proactive preventive posture in the health care setting. Perhaps this will one day also extend to patients in their homes upon discharge from a hospital, many of whom are immune compromised for a specific time frame and others for their lifetime. Water for drinking, showering, bathing and cleaning that is free of harmful microorganisms will provide protection for a growing immunocompromised and aging population as well as increase opportunity for companies that make smart filters, those that are customized to remove specific contaminants, while enabling high throughput.

About the author
Judy Angelbeck, Ph.D. is a senior vice president of Pall Medical. A 20-year veteran with Pall, in her current role she serves as a senior advisor to the Company’s blood business, works on developing new business for Pall technologies in the somatic cell therapy market and provides marketing support on blood and other product areas to the hospital group. Dr. Angelbeck is an appointed voting member of the Blood Safety and Availability Advisory Committee to the United States Secretary of Health and Human Services. She holds a Ph.D. in Cell Biology, a Bachelor of Arts in Journalism and a Bachelor of Science in Biology from the University of Toledo in Ohio. She can be reached via email at


Comments are closed.