Managing the Risk of Waterborne HAIs

Water is essential for life, and we are fortunate to have safe, affordable drinking water from municipal sources. Though water meets drinking standards when it enters a building, the complexity of healthcare building water systems can create conditions that allow growth of microorganisms, including waterborne pathogens that have been linked to healthcare-associated infections (HAIs).

By Eric R. Myers, MS; Henry L. Carbone, MS; Kirsten M. Thompson, BS; and John H. Hanlin, PhD

Water is essential for life, and we are fortunate to have safe, affordable drinking water from municipal sources. Though water meets drinking standards when it enters a building, the complexity of healthcare building water systems can create conditions that allow growth of microorganisms, including waterborne pathogens that have been linked to healthcare-associated infections (HAIs).

Water is increasingly recognized as a vector for infection. A 2002 study suggested that “…perhaps the most overlooked, important and controllable source of nosocomial pathogens is hospital water” where waterborne pathogens were found to cause 43 HAIs between 1966 and 2001. This is critical because water is used extensively in healthcare environments. Potable water is used for handwashing, patient bathing, oral care, and for various medical devices. In 2003, several modes of transmission were cited for waterborne infections including direct contact, ingestion of water or ice, indirect contact (e.g., improperly reprocessed medical devices), inhalation of aerosols dispersed from water sources, and aspiration of contaminated water.

Today the infection prevention literature is replete with evidence linking HAIs to water. Though several Gram-negative pathogens have been found to persist in water systems, the association between Pseudomonas aeruginosa infections and water sources is best understood.(3) Pseudomonas aeruginosa causes infections generalized by inflammation and sepsis, which can be fatal if colonization occurs in critical body organs, such as the lungs, urinary tract or kidneys. There is also abundant evidence linking P. aeruginosa infections and tap water used in the intensive care unit (ICU) and patient rooms:
• A 2001 study found that 74 percent of taps without temperature selection were contaminated with P. aeruginosa.(4)
• A 2002 study used genetic techniques to demonstrate the epidemiological relationship between water isolates and patient infection with P. aeruginosa, finding that faucets were the source of infection for 15 of 45 patients.(5) 
• A 2005 study investigated 132 cases of P. aeruginosa infections using genetic techniques to match strains causing illness to potential sources. Faucets in an ICU were linked to 42 percent of the cases.(6)
• A 2005 study demonstrated that 39 percent of water samples from electronic faucets in hematology units and ICUs yielded P. aeruginosa.(7) 
• A 2007 study used genetic-based epidemiological evidence linking P. aeruginosa with waterborne HAIs. Over a six-month period, 19 out of 38 patient infections were acquired via tap water or cross-transmission.(8)

Other Nosocomial Waterborne Pathogens
Waterborne HAIs caused by other opportunistic pathogens found in water systems have also been documented. A 2013 investigation found that a catheter-related blood stream infection caused by Acinetobacter baumannii was from a showerhead.(9)  In another case, a Klebsiella pneumoniae infection resulted from aspiration tubes being rinsed in tap water.(10) Other reports cite Mycobacterium mucogenicum, Legionella pneumophila, Stenotrophomonas maltophilia, as well as pathogenic fungi such as Aspergillus and Cladosporium as sources of waterborne HAIs.(11-15)

Legionella pneumophila
Legionella pneumophila, the most frequent organism that causes Legionnaires’ disease (LD) is a well-documented waterborne pathogen. It is often linked to healthcare-associated and community-acquired infections. The Centers for Disease Control and Prevention (CDC) cites numerous reports of LD outbreaks in healthcare, including eleven between 2009 and 2010.(16) 

The CDC estimates between 8,000 and 18,000 hospitalizations due to LD occur annually in the United States, with mortality rates of 5 percent to 30 percent.(17)  Legionnaires’ disease can occur when susceptible individuals are exposed to Legionella-contaminated water aerosols (mists) from water sources such as decorative fountains, Jacuzzi/spas, showers, faucets, ice chips (via aspiration) and cooling towers.

Biofilms: Habitat for Pathogens in Building Water Systems
Building water systems can become colonized by biofilm producing microorganisms. Warm water temperatures, complex plumbing loops, periods of water stasis and loss of residual disinfectant such as chlorine create conditions that allow microbial activity and biofilm formation. 

Biofilm is an accumulation of microbial cells that coat surfaces as a slime layer. This dynamic microcommunity often comprises bacteria (including pathogens) algae, yeast and protozoa. Biofilm can be up to four centimeters thick and is a pre-requisite for further microbial growth.(18-19) Alarmingly, organisms within biofilm can be several hundred-fold more resistant to disinfectants than planktonic microorganisms.

Biofilm can be dispersed in a number of ways. Frequently it can be disrupted by high demand and increased water flow rates, by vibration during periods of construction, and by the sudden flow of water from stagnant sections of the water system.(1,18) These events release organisms into the bulk water spreading to faucets and showers where they come into contact with patients, visitors and healthcare workers.

Strategies to Reduce Risk of Waterborne HAIs
Given the evidence that water systems can be vectors for waterborne HAIs, the World Health Organization (WHO) has stated that the “Criteria for drinking water is usually not adequate for medical uses of water.18 Consequently, it is recommended that hospitalized patients at high risk for infection avoid exposure to hospital water and use sterile water. A 2003 CDC guideline highlighted practices to control waterborne HAIs including:(2)
1. Controlling the spread of waterborne microorganisms
2. Prevention of microbial contamination in water systems
3. Remediation strategies for system repairs or emergencies
4. Engineering and infection control measures for preventing LD
5. Considerations for cooling towers and evaporative condensers
6. Considerations for high-risk sources including dialysis water, ice machines/ice, hydrotherapy tanks/pools and medical equipment

Other reported strategies with positive outcomes resulting in reduced waterborne HAIs include a multi-barrier approach. Successful strategies include prevention and control programs such as advanced planning for remodeling or construction, remedial or continuous water disinfection, and application of disposable point-of-use (POU) tap and showerhead water filters in high-risk patient care areas (e.g., burn, transplantation, oncology).(20) 

Given the growing evidence and concern for waterborne HAIs, public health, healthcare professionals and water safety experts are placing greater emphasis on waterborne HAIs from water systems be included as part of the healthcare facility Infection Control Plan (ICP). The ICP interdisciplinary team should include and work in partnership with facilities engineering management who has responsibility for the operation and maintenance of water systems.  Working together, the engineering requirements for managing water systems can then be aligned with the ICP for reducing risk of waterborne pathogens.

There are also published guidelines that describe best practices and engineering strategies for water systems to reduce risk associated with Legionella.(21-22) These strategies are reasonably applicable for reducing risk of other waterborne pathogens. Engineering strategies may include maintenance of water temperatures and residual disinfectant from the city supply water within ranges that suppresses microbial growth. In addition, proper system operation and maintenance, and avoiding water stagnation is required to reduce hazardous conditions that can support microbial growth. Hence, managing these strategies within the context of a defined written water management program is essential for on-going risk management. Important strategies to consider include:
1. Maintenance of engineering controls described above to suppress microbial growth
2. Continuous water treatment using an EPA-approved drinking water disinfectant to control pathogens throughout water distribution
3. Use of POU water filters on taps and showerheads to interrupt infection pathways
4. System surveillance to confirm program effectively controls the identified hazardous conditions; including monitoring of system water temperatures, disinfectant residuals, and waterborne pathogens
5. Regular review to confirm program is being implemented as designed

Creating a water management program to prevent waterborne HAIs may seem complex, but there are many resources available to help guide healthcare facilities through the process. And the benefit of increased patient safety and patient outcomes makes it well worth the effort.

Eric R. Myers, MS, is a senior technical manager for environmental hygiene services at Nalco, an Ecolab company, in Naperville, Ill. He can be reached at
Henry L. Carbone, MS, is a senior product development program leader for Ecolab Healthcare R&D in Eagan, Minn. He can be reached at
Kirsten M. Thompson, BS, is a senior product development program leader for Ecolab Healthcare R&D in Eagan, Minn. She can be reached at
John H. Hanlin, PhD, is the vice president for food safety and public health for Ecolab in Eagan, Minn. He can be reached at


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