Many commercial buildings may be harboring legionella in their domestic hot water systems, potentially causing Legionnaires' disease that goes undiagnosed as pneumonia. Legionnaires' disease was first diagnosed following an outbreak in the Bellevue Stratford Hotel in Philadelphia in 1976. After research into the incident that proved fatal for 34 victims, the bacterium found responsible for the incident was named legionella. Since then, research has indicated that of the approximately 40 species of this organism, Legionella pneumophila is responsible for approximately 90% of the cases fatal to humans. It is estimated that there are between 8,000 to 18,000 cases of Legionnaires' disease each year in the United States and it is possible that many cases go undiagnosed. The fatality rate for this disease is considered to be between 5 to 30%. Those most at risk are elderly, infirm or those with compromised immune systems.

These facts are well known in the commercial building management industry, and as a result building engineering departments go to great lengths to manage these water supplies safely, with water treatment programs designed specifically to ensure these water supplies are hostile to the growth of legionella including chemical treatment with chlorination or other compounds. Less well known is the ability of legionella to lodge in domestic water supplies where chlorine concentrations will be lower, and water temperatures are kept at levels that would preclude scalding building users. Legionella will grow in water at temperatures from 68 °F to 122 °F. The upper end of this range is where many commercial buildings deliver hot water to bathrooms. HBI has reviewed recent studies on prevalence of legionella from this source, and it may come as a surprise how frequently this organism is growing in building water supplies.

Literature Review of Prevalence of Legionella in Potable Hot Water Systems

To understand the prevalence of this organism in domestic water supplies, we conducted a review of the available published literature on the prevalence of legionella in domestic water systems of commercial buildings. The potential for legionella to occur in domestic water supplies inside buildings was illustrated in a British study in the early 1980’s which found that about 60% of cold and hot water systems contained Legionella, including hotels, hospitals and commercial office buildings. 55% of hot water systems and 13% of cold water systems were found to be positive for legionella. We looked at more recent data that was as relevant as possible to US commercial buildings. We have prepared a spreadsheet, available on our website that shows a summary of these findings. As seen in this spreadsheet, those published studies show legionella is frequently found in domestic water systems of all types. In fact we did not find a single study where no legionella was found in these systems.

This current lack of published data in the US in particular indicates that there is likely to be a general lack of awareness in the building engineering industry of the likely prevalence of legionella in commercial building domestic water systems, and that there is a need for more frequent monitoring of the organism from these sources. A common theme of the papers we reviewed was a close association between water supply temperatures and legionella concentrations. Because of the concern over liability for scalding building occupants, especially in our litigious American society, it is possible that many water systems are likely to be kept at temperatures favoring legionella growth. Moreover buildings in warm or hot regions of the United States may be more susceptible than areas with cold climates. We conclude that the presence of legionella in domestic water systems of commercial buildings of all types in the USA is likely to be extremely common.

Solutions

If, following testing for the presence of this organism, legionella is found in your water system, the resolution and prevention of this problem can be fairly simple. The system can be pasteurized by raising the hot water temperature for a set period of time, or it can be chemically treated. Options include dosing with chlorine dioxide or metal ions (silver or copper), as well as cleaning plumbing components where scale accumulates. Contact HBI for further diagnosis or treatment consultation.

Country

Pub.

Date

Water source

Building type

# of samples

+ve Samples

+ve buildings

Leg types

Reference

Japan 2001 Bath 50 Homes for Elderly 14 37.0% 28.5% L.Pn 100% Yamamoto et al

Italy Domestic hot water Varied 146 22.6% Leg. Spp Borella et al

Italy 2005 Domestic Hot water 40 Hotels 119 60.0% 75.0% L.Pn 87% L.Pn s.g.1 45.8% Borella et al

Japan 2002 Whirlpools Homes 2895 (including cooling towers) 71.0% L.pn s.g.5 34% L.pn s.g.3 22% Suzuki A.A. et al

Clubhouses 63.0%

Dormitories 62.0%

Homes for Elderly 51.0%

Hotels 30.0%

Germany 2005 Domestic water 2 Hospitals 210 25.2% Leg. Spp Vonberg R.P. et al 32 93.8%

Italy 2005 Domestic hot water 5 Hospitals 32 93.7% Leg. Spp 40% Leg. Pn 33.3% Leoni E. E. et al

11 Hotels 46 60.9%

59 Apartments 59 41.9%

Italy 2002 Domestic hot water 11 Hospitals 121 100% 100% Leg. Spp 86.8% Leg. Pn 82.6% Legnani P. P. et al

USA 2006 Domestic hot water 53 buildings 60% Leg spp Flannery B.B et al

Turkey 2005 Domestic hot water 24 hotels 168 65.5 91.7% L.pn s.g.1 Uzel A.A. et al

Spain 2001 Domestic water 20 hospitals 186 37.0% 85.0% Leg pn. Sabriagrave M.M. et al

Italy 2001 Domestic hot water shower heads 12 Swimming facilities 48 56.2% Leg. Spp 62.9% Leg. Pn 70.3% Leoni E. E. et al

Sardinia Domestic water 9 Cruise ships/ ferries 90 42.0% 85.70% Leg. Spp 42.0% Leg. Pn 95.5% Azara A.A.

USA 92-94 Domestic hot water Varies 73 12.0%

Clayton Potable water 184 7.0%

N.Z. 2000 Domestic hot water 100 Homes 100 0-12%** Leg. Spp Bates, MN et al

References

Yamamoto A study on contamination from Legionella spp. at a home for the elderly in Toyohashi City. Nippon Koshu Eisei Zasshi 2001 Nov;48(11):914-22.

Borella P.P. et al. Legionella infection risk from domestic hot water. Emerg Infect Dis 2004 Mar;10(3):457-64.

Borella P.P. et al. Legionella contamination in hot water of Italian hotels. Appl Environ Microbiol 2005 Oct;71(10):5805-13.

Suzuki A.A. et al Occurrence of Legionella bacteria in a variety of environmental waters--from April, 1996 to November, 2000. SB - Kansenshogaku Zasshi 2002 Sep;76(9):703-10.

Vonberg R.P. et al. Use of terminal tap water filter systems for prevention of nosocomial legionellosis. J Hosp Infect 2005 Jun;60(2):159-62.

Leoni E. E. et al. Legionella waterline colonization: detection of Legionella species in domestic, hotel and hospital hot water systems. J Appl Microbiol 2005;98(2):373-9.

Legnani P. P. Legionella contamination of hospital water supplies: monitoring of private healthcare facilities in Bologna, Italy. J Hosp Infect 2002 Mar;50(3):220-3.

Flannery B.B et al. Reducing Legionella colonization in water systems with monochloramine. SB - Emerg Infect Dis 2006 Apr;12(4):588-96.

Uzel A.A. et alPrevalence of Legionella pneumophila serogroup 1 in water distribution systems in Izmir province of Turkey. APMIS 2005 Oct;113(10):664-9.

Sabriagrave M.M. Environmental cultures and hospital-acquired Legionnaires' disease: a 5-year prospective study in 20 hospitals in Catalonia, Spain. SB - Infect Control Hosp Epidemiol 2004 Dec;25(12):1072-6.

Leoni E. E.. Prevalence of Legionella spp. in swimming pool environment. Water Res 2001 Oct;35(15):3749-53.

Azara A.A.. Prevalence study of Legionella spp. contamination in ferries and cruise ships. BMC Public Health 2006;6:100.

Clayton Group Services. Clayton Group Services Presentation. Bates, M.N. et al. Investigation of the prevalence of Legionella species in domestic hot water systems. New Zealand Medical Journal 2000, vol. 113, no1111, pp. 218-220.