Professor POU/POE: Legionella revisited

Oct. 1, 2015

Legionella bacteria are common in many environments, including soil and water, and at least 50 species and 70 serogroups have been identified.

Q: Why hasn’t the U.S. Environmental Protection Agency (EPA) provided practical guidance to facilitate supplemental disinfection, especially in hospital/health care facility plumbing, and updated its regulation that discourages supplemental disinfection?

A: It is an obvious need and long overdue. To protect public health and reduce the risk of waterborne legionellosis disease and deaths, it should be a high priority.

More legionellosis outbreaks, cases and deaths caused by Legionnaires’ disease continue to be reported periodically worldwide and continue to increase. The Centers for Disease Control (CDC) published its most recent Morbidity and Mortality Weekly Report (MMWR) for waterborne disease outbreaks on Aug. 14, 2015, for the period of 2011 to 2012. It included two earlier outbreaks that were not reported in the MMWR for the period of 2009 to 2010. The CDC defines a waterborne disease outbreak as two or more persons (cases) linked epidemiologically by time and location of water exposure, illness characteristics, and with water exposure implicated as the probable source of the illness.

Legionella bacteria are common in many environments, including soil and water, and at least 50 species and 70 serogroups have been identified. Legionella bacteria-related respiratory diseases include legionellosis caused by Legionella pneumophila, and Pontiac fever, a less virulent disease caused by Legionella longbeachae. The CDC reports are undoubtedly understatements of the actual numbers of outbreaks, cases and deaths because of underreporting and difficulties in diagnoses without the genotyping and serotyping of the disease organisms.

The 2011-2012 MMWR results are similar to the previous 2009-2010 report. The MMWR listed 431 cases of 10 microbial diseases, plus one chemical incident from a cross connection, and 102 hospitalizations. Twenty-one outbreaks were caused by Legionella, resulting in 111 cases cited in text (table totaled 125 cases) and 14 deaths. Once again, Legionella was the only cause of the deaths. Legionella cases occurred in hospitals, long-term care facilities, hotel/motel/ lodge/inn and apartment/condo locations. Hospital/health care and long-term care facilities accounted for 80 cases and 12 deaths. The hotel/motel/lodge/inn category had 35 cases and two deaths while 10 cases and one death occurred in apartments/condos.

In addition, public health officials from 11 states reported 18 outbreaks associated with environmental or undetermined water exposures, causing 280 cases of illness, 67 hospitalizations (24 percent of all cases) and 10 deaths. These included 15 legionellosis outbreaks that resulted in 254 cases and all 10 deaths. The legionellosis outbreaks occurred in four hotels and motels, three hospitals and health care facilities, three long-term care facilities, an indoor workplace/office, a factory/industrial setting, a mobile home park, a resort and a multiuse facility.

Five legionellosis outbreaks had a known water source, including three from ornamental fountains, a cooling tower and a storage tank. The water source was undetermined for 10 legionellosis outbreaks. Among these, one outbreak had multiple implicated sources (drinking water, a spa and a cooling system), and the remaining nine had insufficient data to determine a particular source. Five of the 10 deaths caused by Legionella were associated with a health care facility, including two long-term care facilities, two with hospitals, and one was an unknown type of health care facility.

New York City’s legionellosis outbreak

The cooling tower in a recently renovated hotel in the South Bronx seems to have been one of at least five possible sources of Legionella bacteria contamination from aerosols in the area. Since early July, 113 cases have been reported with 12 deaths. The mist created from the heat exchange process and blowers can be a carrier of the bacteria. Numerous building cooling towers in the area were tested and several contained the same serotype that was present in infected patients. The cooling towers have been disinfected. The city announced on Aug. 20 that no new cases of legionellosis had been reported and declared the outbreak over. Other legionellosis outbreaks with illnesses and deaths were recently reported in a California prison and a veterans home in Quincy, Illinois, in late August.

International legionellosis surveillance and outbreaks

Contracting legionellosis is a risk factor anywhere in the world because of the ubiquitous environmental sources, but it is likely much more dominant in the developed world with its aerosol sources from indoor plumbing, water-based cooling towers, hot tubs and spas, and concentrations of patients in hospitals and nursing homes.

The European Center for Disease Prevention and Control (ECDPC) maintains two reporting systems for disease cases, but again, cases are likely to be underreported. Nevertheless, it probably provides the best available data on legionellosis incidence among developed country populations where living and environmental conditions are similar to the U.S. In 2013, 5,851 cases were reported by the 28 European Union (EU) states and Norway. Six countries (France, Spain, Italy, Germany, the Netherlands and U.K.) accounted for 83 percent of the reports, but that might be closely associated with the diligence of reporting compliance. The actual case numbers are likely much greater. About 160 cases reported without specifying the laboratory analysis method were excluded from the statistics.

People older than 50 accounted for 81 percent of the cases, with a median age of 63, and the male to female ratio was 2.4 to 1, which might reflect higher smoking frequency among males. The death rate was about 10 percent of cases. Most cases were community acquired and 19 percent were associated with travel. Travel-associated cases, which accounted for 787 of the cases, were reported by 30 EU/ European Economic Area (EEA) countries, Canada, Israel, Turkey, Thailand and the U.S.

Legionellosis reporting has been underway since 1995. The trending of reported EU/EEA cases began at about 4 per million population in 1995, rose steadily to about 12 per million in 2005, and has been relatively stable from 2005 to 2013. That is possibly surprising, but it might also reflect the limitations of the reporting compliance. Cases were consistently more concentrated in the warmer months between August and October, and that cycle has been repeated each year from 2008 to 2013. Mortality rates increased with age, were greater for cases acquired during the winter months and peaked in February.

Another potential risk factor

Another risk factor may be ice machines. The possibility that chewing contaminated ice could lead to aspiration of the microorganisms needs to be examined. Icemaker water reservoirs are often located near compressors, the heat from which could warm the water to temperatures in which Legionella growth could occur during low-use periods, and then they could become entrained in the ice.

Regulatory issues

The current federal and state regulatory environment is an impediment to many facilities installing supplemental disinfection in the drinking water systems, because EPA drinking water regulations require that if any facility with more than 25 users adds water treatment to the public water entering the facility, it becomes a public water system. Therefore, an apartment building or nursing home with permanent residents would become a community water system, and a hospital with 25 employees would become a non-transient, non-community water system. Monitoring and other associated requirements would be commensurate with their regulatory status. States have taken different positions on those situations. My anecdotal information from talking with several state authorities is that they range from not wanting reporting if a hospital were adding supplemental disinfection, to placing minimal requirements, to imposing substantial requirements on the facilities. These requirements could range from monitoring for specific components, such as disinfectant residuals and coliform bacteria, to corrosion indicators and some other maximum contaminant levels (MCL), to broader monitoring, requiring certified operators, formal reporting including public notifications, to preventing the use of some disinfectants such as copper and silver, which are used successfully in numerous locations.

An MCL goal of zero and a treatment technique requirement for Legionella under the 2006 Surface Water Treatment Regulation applies at the water treatment plant. Treatment for Giardia and virus removal is also expected to remove Legionella. However, Legionella and other regrowth microorganisms result from conditions in the distribution and the plumbing systems. Reseeding of the systems might occur in several situations:

  • If a few microorganisms survive water treatment
  • From soil contamination in water line leaks and breaks
  • During plumbing repairs
  • New construction in which the plumbing system has not been properly disinfected prior to commissioning and the facility’s placement into service

Based on comments during an EPA water conference that I attended last year, states are asking for EPA guidance, and many are not making decisions while awaiting a formal statement from the EPA. Apparently, historical discretion has been allotted to states on their interpretations of the regulations. Some state officials said that they had not required formal drinking water system status for introducing some technologies, such as central water softening. If that is the case, then allowing supplemental disinfection would certainly be appropriate, where a clear public health benefit is the purpose.

At the time of publication, the EPA has operated a working group for about two years with the goal of producing national guidance, which, however, would not be mandatory. Release of a review draft is likely this fall. It is not obvious why such informational, non-mandatory guidance has required so much time to complete, when the public health risks are real and obvious, the need is apparent, and the options are well-understood. Guidance would at least provide water management recommendations that states and facilities could follow and the opportunity for some degree of national consistency. More than a year ago, I wrote a rather comprehensive paper on the topic with specific recommendations titled "Facilitating Supplemental Disinfection for Legionella Control in Plumbing Systems" in Journal American Water Works Association 106:8, 74-83, August 2014. Take a look. The choices and consequences are clear.


The EPA’s opportunities to regulate Legionella in plumbing systems are likely limited since its authority under the Safe Drinking Water Act for private facilities is limited. That was tested and restricted by the appellate court from a challenge to the Lead and Copper Rule for corrosion control.

Perhaps the EPA’s best choice in the interest of public health would be to propose and promulgate a simple modification of the existing implementation regulations under the Safe Drinking Water Act to allow supplemental disinfection without unnecessary stipulations. The original regulation was issued more than 30 years ago when Legionella and other regrowth issues were not contemplated. In the interim, the American Society of Heating, Refrigerating and Air-Conditioning Engineers has issued DWA Standard 188-2015, Legionellosis: Risk Management for Building Water Systems. This standard’s implementation should provide some level of risk reduction.

The CDC emphasizes follow-up after outbreaks rather than prevention that would include aggressive monitoring to identify system contamination and applying cleaning and disinfection to reduce the potential for illnesses to occur. The relationship between water or biofilm Legionella concentration and risk of infection is not understood, but regular water quality surveillance and maintenance in high-risk facilities would reduce risks. In the Aug. 14, 2015, MMWR, the CDC calls for expanded partnerships between public health, regulatory and industry professionals to develop and use regulatory and nonregulatory approaches to address groundwater and building plumbing system deficiencies to prevent outbreaks. Perhaps a more explicit recommendation for water quality and system biofilm monitoring at least in high-risk facilities would encourage more preventive activity sooner.

Editor’s note: This is an update to the May 2014 Professor POU/POE column on Legionella in Water Technology and on Dr. Cotruvo thanks David Swiderski from Terra Marra International for information he provided during the writing of this column.

Dr. Joe Cotruvo is president of Joseph Cotruvo and Associates, LLC, Water, Environment and Public Health Consultants. He is a former director of the EPA Drinking Water Standards Division.

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