Municipal water treatment processes do not remove all microbes from drinking water; among the survivors are Legionella. As water flows through pipes, bacteria of all kinds attach to rough surfaces. Here, the bacteria flourish and multiply, adding layer upon layer of a glue-like slime coating in the pipe. This substance, together with its resident microorganisms, is called biofilm.
Legionella and other bacteria thrive in biofilm, which is impervious to most biocides. From time to time, pieces of biofilm break off and make their way out of the system through a faucet or showerhead. The microscopic, pathogen-rich particles aerosolize and can be inhaled. According to estimates by Dr. Victor Yu, renowned Legionnaires' expert, 70 percent of hospital water systems are likely colonized by Legionella bacteria. The immune compromised are most susceptible to Legionnaires' and other diseases caused by waterborne pathogens. Legionnaires’ disease has a reported mortality rate of up to 30%.
In long term studies at the Johns Hopkins Medical Institutions, chlorine dioxide has been shown to be highly effective in eliminating bio film and associated pathogens, such as Legionella, from hospital water supplies.
Tap water is a documented source of infections, such as Legionnaires Disease (LD). Waterborne organisms of primary concern include Legionella pneumophila, the causative agent of LD, as well as Pseudomonas aeruginosa, Acinetobacter and Stenotrophomonas maltophilia.
Colonization of building water systems is closely associated with “biofilm”, a complex aggregation of microorganisms marked by the excretion of a protective and adhesive matrix (slime).
Biofilm plays a key role to the proliferation of waterborne pathogens; it is ubiquitous in water environments and is found on most surfaces that are in prolonged contact with water, including the inside of both hot and cold water pipes in buildings. Municipal drinking water treatment processes do not kill all the microorganisms in the water, and do not prevent downstream development of biofilm.
Legionella pneumophila reportedly colonizes approximately 70% of large plumbing systems. Pseudomonas aeruginosa, the causative agent of pseudomonas pneumonia, is one of the most common pathogens in the health care environment, and is present in an estimated 40% of institutional water pipes. Infections in healthcare environments (nosocomial infections) associated with these organisms have a mortality rate of about 40%.
Most waterborne nosocomial infections are associated with drinking the contaminated water or via inhalation and/or aspiration. An individual may inhale aerosols, fine sprays, mists or other microscopic droplets of water contaminated with pathogens (e.g., from a shower), providing direct access into the lungs. Aspiration may occur when choking or spontaneously during drinking, ingesting, and swallowing. Patients that have been recently intubated are at high risk of aspiration-based exposure because the process allows oral fluids and particles to by-pass natural gag reflexes and enter the respiratory tract and lungs instead of the esophagus and stomach.
While relatively healthy people may contract waterborne infections, such as LD, the most susceptible people are over 55 years old, infants, cigarette smokers and those on immunosuppressive therapy and with some other atypical medical conditions. Taken together, these groups constitute more than 25% of the population of the United States. In hospitals and long-term care facilities, the percentage of persons who are at risk is higher.
