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About Legionella

Legionella Overview

Common infections caused by Legionella are Legionnaires’ disease (LD), a severe pneumonia, or Pontiac
Fever, a flu-like illness. However other species (i.e., L. micdadei, L, longbeachae) can cause LD as well.
L. pneumophila has many subgroups called serotypes. L. pneumophila serotypes 1, 3, 5, and 6 have been
the causative agents of Legionnaires’ Disease. Co-infections with different species and/or serotypes have



Legionella are commonly found in aquatic environments and some species have been found in soil.
The organisms are found in a wide range of environmental conditions and are relatively resistant to
low pH, dissolved oxygen levels, and routine chlorination techniques for drinking water. Temperatures
above 104° F promote rapid multiplication of the organism. The organisms are consistently found in
the biofilm that forms in aquatic environments, cooling towers and potable water systems.



The health risk factors for legionellosis are people who are immunocompromised by an underlying medical condition, those taking immunosuppresive drugs, heavy smokers, those who have chronic lung conditions, and the elderly. Several studies have documented cases of pediatric legionellosis in children under 1 year of age or children with underlying medical conditions such as malignancy or immunosuppression. Legionellosis is not contagious; there is no evidence that the disease can be transmitted from person to person. Exposure must be through inhalation or aspiration of contaminated, aerosolized water. Once a person has Legionnaires’ disease, getting it a second time is extremely rare.


Monitoring Guidelines

As a result of the Legionnaires’ disease outbreak that occurred in the Bronx in August of 2015, both the State of New York Department Health and New York City Department of Health and Mental Hygiene have passed the first US regulations specifically for testing cooling towers (and drinking water water systems in hospitals) for Legionella. These regulations specify action levels requiring cooling tower disinfection. In addition the US Centers for Disease Control and Prevention (CDC) recommends routine monitoring for Legionella in all bone marrow and organ transplant hospitals nationwide. Routine monitoring in healthcare facilities is recommended or required in several states such as NY, TX, MD, Los Angeles County and Allegheny County PA. Canada has guidelines for monitoring healthcare facilities. In June, 2015 The American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) passed ASHRAE Standard 188 for the prevention of Legionellosis in buildings. While this voluntary standard of practice doesn’t specifically address Legionella testing, it offers basic recommendations for establishing a building water system safety plan.


Sampling And Analysis

Take a 1000mL sample for potable water and a 250mL sample for nonpotable water. Be sure to use sterile bottles with a chlorine neutralizing agent. Since biofilms are the actual reservoirs for the bacteria it is also recommended to take sterile swab samples of biofilm in areas where it is present. Samples should be shipped overnight to the lab on freezer packs. Culturable analysis either by the US Center for Disease Control or the International Standard Organization is the “gold standard” and requires 10-14 days. Testing by Polymerase Chain Reaction (PCR) takes 2-3 days and may be very useful for providing fast, presumptive results to reduce liability during an outbreak. Testing by Next Generation DNA Sequencing can provide evidence that compares the molecular fingerprint of an environmental isolate to a clinical isolate. Isolating Legionella from environmental samples is difficult. Make sure to use an experienced lab that is either CDC ELITE or HPA (United Kingdom) proficient.


An Overview of Legionella Analyses - Background

The first recognized outbreak of Legionnnaires’ Disease occurred in the US at the American Legion Convention in Philadelphia during the summer of 1976. There were several hundred people who were stricken. Thirty four people died from the disease. As a result of the efforts of the US Centers for Disease Control and Prevention (CDC), this was the first time the bacteria was cultured and identified. Earlier outbreaks of the disease went undiagnosed. Since that time, there have been many identified outbreaks in this country and abroad prompting professional organizations and health departments worldwide to implement guidelines for diagnosing and reporting the disease, and monitoring the organism. However, there are no health standards for safe levels of exposure to Legionella.


Transmission and Epidemiology

Ubiquitous in all aquatic environments, Legionella bacteria are found in groundwater as well as fresh and marine surface waters. The bacteria enter our plumbing systems, whirlpool spas, and cooling towers via these water sources. Unless control measures are conducted properly and routinely, the biofilm, scale, and corrosion that builds up over time in these systems will protect the organism and allow it to multiply.


Contaminated aerosolized water from cooling towers, whirlpool baths, nebulizers, faucets, and showerheads becomes airborne. When a susceptible host inhales the contaminated aerosol, legionellosis can occur. Aspiration of the contaminated water can also cause the disease. Legionellosis can cause two types of illness: 1. a severe form of pneumonia (Legionnaires’ Disease) often accompanied by serious

long term health effects, and 2. a mild flu-like illness called Pontiac Fever. Other infected organs, and asymptomatic infections may also occur.


Historically, risk factors for getting the disease included age, gender (males), compromised immune systems, and pre-existing medical conditions such as chronic obstructive pulmonary disease, cancer, diabetes, and the use of rheumatoid arthritis drugs and chemotherapy. Men over 65 years of age who were heavy smokers and drinkers were identified as being at greatest risk. While that is still true, recent research from Neil and Berkelman at Emory University has identified an abrupt increase in the incidence of Legionnaires’ Disease in the US in all age groups in the last 20 years. This trend has also been noted internationally by other researchers. They have noted an overall increase in the disease among all people aged 45 to 64. Rates of disease in males still exceed the rates in females.


There have also been cases of the disease in healthy, younger people. Premature, immuno-compromised, or ventilated neonates are at risk from hospital-acquired infection. In addition, cases have been reported in children aged 15-19 years old. Although the disease is under-reported, travel (cruise ships), hotel, and resort related outbreaks are reported each year. These are mostly associated with the outbreaks involving cooling towers and whirlpool spas receive the most media attention, studies prove that building potable water sources account for most of the infections. This is particularly true in hospitals and nursing homes where there are large numbers of immunosuppressed or critically-ill people. For these reasons, many state health departments have guidelines that recommend routine monitoring for Legionella in critical-care hospitals and nursing homes. In 2008, the Veteran’s Administration promulgated a directive which requires all VA hospitals and rehabilitation centers to implement monitoring for the bacteria in their potable water systems.


Choosing Sampling Methods

Proper methods for collecting and analyzing samples are necessary to ensure defensible results. Since the bacteria in water are present in very low levels, 1000 mL potable water samples are recommended by the US Centers for Disease Control and Prevention (CDC). This sample size allows for the bacteria in the water to be concentrated, allowing for better detection in potable water samples. Many professional guidelines recommend semi-annual sampling for potable water sources. In non-potable water sources such as cooling tower water, a 250 mL sample size is sufficient. Professional guidelines suggest these sources be monitored quarterly. Sampling should be conducted in a way that maximizes recovery of the organism. Legionella samples should be collected wherever water aerosolization may occur. Sampling aerosolized water alone, however, will likely miss the real source of the organism. This source is the biofilm or slime that is often found in our plumbing systems, cooling towers, and whirlpool baths. There is no correlation between Heterotrophic (aerobic) plate counts (HPC/APC) and Legionella. Therefore, HPC testing should not be used as a surrogate for Legionella testing. Routine Legionella testing will identify a potential exposure risk. The


Where to Look for Legionella

When conducting your building water system investigation, walk-through, or risk assessment use this section to help you identify all potential Legionella reservoirs in the building. If conducting an investigation due to a suspected case or outbreak, also survey the surrounding neighborhood to identify any cooling towers, wastewater treatment facilities, storm water/gray water re-use facilities (i.e. golf course spray irrigation water systems), or ornamental fountains that may be located near the building in question. If necessary, obtain permission

to sample these off-the-property locations. Also identify and visually inspect all the building fresh-air intakes/pedestrian walkways with respect to these neighborhood locations.

1. Potable water systems

2. Cooling towers

3. Water walls

4. Aerosol generation during the biological treatment of some industrial process wastewater streams ie., pulp and paper manufacturing,
food and beverage manufacturing, pharmaceutical manufacturing

5. Aerosol generation during municipal water and wastewater treatment

6. Raw, utility or fire water

7. Ornamental outdoor and indoor water fountains and ponds

8. Heated swimming pools

9. Hot tubs

10. Humidifiers/CPAP Machine Water Reservoirs

11. Metal working fluids

12. Medical therapy equipment like dialysis units, nasogastric tubes, respiratory equipment and nebulizers, whirlpool baths

13. Commercial car wash facilities particularly those using recycled water

14. Supermarket vegetable misters

15. Ice machines in hotels and hospitals

16. Outdoor body misters at ballparks and amusement parks

17. Use of tap water in place of manufactured windshield cleaner fluid

18. Fog Machines

19. Ultrasonic Dental Descalers

20. Storm water/gray water spray irrigation systems

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