Legionella Information Overview

About Legionella:

Legionella Testing LabLegionella is a bacterium that is naturally found in water, although it grows best in warm water. Some species have been known to cause diseases in humans, notably Legionnaires’ Disease and Pontiac Fever, though any disease caused by the bacterium is referred to as legionellosis. Transmission of Legionella is not passed from person to person; rather, it is contracted when the person inhales a droplet nuclei in mist or vapor containing the bacteria.

Reported cases of Legionnaires’ disease have steadily increased in the United States from 400 cases per year in the 1990’s to 4200 cases in 2011, according to the Centers for Disease Control and Prevention (CDC). Scientists believe the actual number of cases is between 50,000 and 100,000, because many cases of unreported pneumonia are actually caused by the bacterium that causes Legionnaires disease. Most cases of illness are caused by Legionella pneumophila, Serogroup 1. Legionnaires’ disease is a type of pneumonia that affects the lungs and is often fatal. Individuals most likely to develop Legionnaires’ disease are those with compromised immune systems or lung problems, such as smokers, the elderly, the very young, and chemotherapy patients.

The Organism:

Legionella are gram-negative rods and require selective media to grow. These are mesophilic bacteria (35-37°C). To date, there is 50 known species of Legionella and about 70 serogroups have been recognized to cause disease in humans. The most common species of Legionella that causes legionnaire’s disease is Legionella pneumophila Serogroup 1.

Documented Cases of Legionnaires’ Outbreaks:

In Reynoldsburg, Ohio, there have been thirty-nine cases of Legionnaires’ disease confirmed among residents, visitors, and employees of the Wesley Ridge Retirement Community, with six individuals dying since the beginning of July 2013.

In June 2013, Legionella pneumophila was found in 18 health facilities in the state of Queensland, Australia, including a hospital in Brisbane where one man, age 66 died from the illness.

The House Committee of Veteran Affairs (VA) is currently investigating the VA Hospital system concerning Legionnaires’ disease outbreaks, leading to 21 illnesses and five deaths.

In November 2012 an outbreak of Legionella pneumophila in Quebec City government buildings resulted in 180 cases of LD and 13 deaths.

Testing Regulations (ASHRAE 188-2015):

The American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) finalized a standard for the prevention of legionellosis associated with building water systems, ASHRAE 188-2015, “Legionellosis: Risk Management for Building Water Systems.” The standard covers which buildings should be subject to Legionella screening, where to screen, and lays out the responsibilities of building managers and facilities equipment personnel and the development of a water risk management program.

Conditions That Promote Legionella disease causing bacteria (LDB):

  • Stagnation and dead loops
  • Warm temperatures (between 20° and 50° C)
  • pH between 5.0 – 8.5
  • biofilm sediment

Where to Test:

Legionella Sources

Any water sources in a building could be a reservoir for Legionella, if conditions are conducive to LDB growth. Some of the more common places in the water system that harbor LDB are:

  • Cooling towers, evaporative condensers, and fluid coolers
  • Holding tanks, cisterns, and water softeners, and domestic hot water heaters for potable water
  • Decorative fountains
  • Whirlpools and spas
  • Humidifiers
  • Ice machines
  • Shower heads/faucets or taps
  • Misters
  • Fire sprinkler systems

Other areas that could be tested include drinking fountains, eyewash stations, respiratory therapy equipment, and any other area in either a private or public water system. It is important to map out the water system from point of origin to all possible reservoirs when testing for LDB.

Important Facts about Sampling:

Always wear a respirator when testing suspected Legionella sources. There are two main ways to test for Legionella:

  • Direct water sample: If taking a direct water sample, collect between 250 mL to 1 L of water. Be sure to use an appropriate neutralizing agent if the water has been subjected to a chemical disinfectant.
  • Arrive in laboratory within 72 hours. Do not send water over weekend.
  • Swab Method: Use pre-packaged, sterile swabs and transport in the container they came with, may include water associated with sample (shower, sink, etc.)
  • For additional sampling please see OSHA’s Water Sampling Protocol
To learn more about Legionella testing and our related services please request information using the form here or call us at (877) 648-9150. Thank you!

Sampling Procedures:

Water Samples

legionella water analysis

Water samples are the practical way to sample for Legionella. Legionella counts will be more accurate in water than air and testing will indicate the potential risk for exposure. When sampling for Legionella always use a sterile container containing sodium thiosulfate. Samples should be kept cool and overnighted to the lab for analyses. Samples should be received at the laboratory no later than 72 hours from sampling.

Non-Potable Water Systems
Cooling Towers and Evaporative Condensers

Samples can be collected in a sterile 250 mL bottle containing sodium thiosulfate. When collecting from the reservoir the bottle should be inverted under the water and moved in a single direction. Try not to collect excess sediment in the water samples.

Decorative Fountains, Hot Tubs, Fire Sprinkler Systems, Cisterns, and Humidifiers

Samples should be collected in a 250 mL bottle containing sodium thiosulfate. Include water from the bottom and near the sides of the reservoir.

Potable Water Systems
Hot Water Systems

Two samples should be taken when sampling a hot water system. A pre flush sample and a post flush sample. When collecting the pre flush sample, turn the hot water tap on immediately collect the first 250 mL of water containing sodium thiosulfate. Sinks, showerheads, hoses, or bottom of hot water tank are all places samples can be taken. When collecting the post flush sample, allow the water to run for 1 full minute or until water sample is hot then collect sample in a 250 mL bottle containing sodium thiosulfate. By pulling two samples you can determine if the contamination is at the fixture or from the supply water in the plumbing lines.

Cold Water Systems

Cold water systems can be analyzed by collecting the first draw sample. Drinking fountains, faucets and showerheads are the appropriate outlets to sample. Collect 250 mL of water in sterile container containing sodium thiosulfate.

For testing Legionella in domestic waters like drinking water, water coolers, chillers, eye washers etc, samples may be collected in sterile 250 ml to 1 Liter bottles with sodium thiosulfate. The 1 Liter bottles are available from the lab upon request for a charge.



Swab sampling is a method recommended to be done alongside water samples. Results from surface samples may show Legionella but will not reflect the concentration of Legionella in the water under normal conditions. Swabs of biofilms from faucet aerators and showerheads can yield Legionella on culture from potable water systems. Samples should be taken from both the hot and cold-water faucets before running the water for sample collection. HVAC systems can be checked for the presence of the Legionella by swabbing the condensate pan, cooling coils and humidifier.

Sterile swabs can be obtained from the laboratory free of charge. Swabs should be rubbed vigorously over the surface being sampled. Collect at least 250 ml of water from same site into sterile container and place swab and water together. Treat as one sample. Keep swabs cool when transporting to the laboratory. Swabs should be returned to the laboratory within 72 hours of collection.


Air sampling is not recommended as a stand-alone test due to fact that the bacterium has a short lifespan in air. Air samples can demonstrate the presence of Legionella in aerosol droplets but can produce false negative results. A quantitative air culture can be obtained by using an impactor type sampler, such as the Surface Air Sampler (SAS), Andersen and rotary vane pump, or other studied impactors. When air samples are taken, a three-plate protocol is recommended consisting of Buffered Charcoal Yeast Extract Agar (BCYE), BCYE with antibiotics and Blood Agar. A 15 minutes sample at 28.2 liters per minute with an Andersen or a 4 minute sample with a SAS at 100 lpm is recommended by the CDC guideline document.


Bulk samples can be test for Legionella. Often samples are sludge from the bottom of a condensate pan scraped off a cooling coil. Samples should be collected in a sterile container, kept cool and transported to the laboratory within 24 hours of collection.

Click here for sampling protocols.


Use of control measures like:

  • Industrial hygiene practices and maintenance procedures.
  • Routine environmental monitoring
  • Effective disinfecting methods that include chlorination, ozonation, use of ultra violet, heat-flush (heat shock) method and copper silver ion systems.

CDC Elite Certification:

The ELITE Program certifies labs in the isolation of Legionella from water samples. Labs that perform adequately receive a Certificate of Proficiency that indicates that the lab’s procedures are consistent with federal recommendations and that they meet or exceed typical industry standards for recovery of Legionella.

Aerobiology follows CDC culture method for Legionella analysis. The culturable method remains the “gold standard” for the recovery of Legionella. After testing, send to one of our six CDC ELITE certified laboratories for analysis. Include the site tested and date /time of collection. We have CDC Elite laboratories located Nationwide in Washington, D.C., Cherry Hill, NJ, Atlanta, GA, Denver, CO, Phoenix, AZ, and Los Angeles, CA.

Click here for sampling protocols.


Government Guidelines and Online Resources

The subject of Legionella has been in the news and on the radar screens of government agencies and professional associations. Here we hope to provide you with a summary of Legionella related guidelines and online resources that can help investigation and treatment of the deadly bacteria.

CDC devotes a section on its website providing information on Legionnaires’ Disease and Pontiac Fever (http://www.cdc.gov/legionella/index.html) and has developed a series of six videos that discuss Legionella ecology, environmental assessments, how to develop a sampling plan, and how to collect the most common sample types. Here is the link: http://www.cdc.gov/legionella/videos.html.

Developing a Water Management Program to Reduce Legionella Growth & Spread in Buildings
A Practical Guide to Implementing Industry Standard
Source: CDC.gov – June 5, 2017

US EPA has guidelines about maintaining the quality of water in building distribution systems, including a review of disinfection technologies with a focus on Legionella. These materials are currently available for public review: http://www2.epa.gov/dwsixyearreview/drinking-water-distribution-systems

OSHA‘s website has a comprehensive took kit for Legionella monitoring, sampling, and response actions: https://www.osha.gov/dts/osta/otm/legionnaires/index.html

ASHRAE published a new standard on Legionella: ANSI/ASHRAE Standard 188-2015 Legionellosis: Risk Management for Building Water Systems

AIHA releases a new guideline on the Recognition, Evaluation, and Control of Legionella offers guidance for industrial hygienists and other occupational and environmental health and safety (OEHS) professionals on assessing building water systems before disease occurs. https://www.aiha.org/marketplace/Pages/Product-Detail.aspx?productid={3A823505-FEF3-E411-A28B-005056B20848}

HHS: Centers for Medicare & Medicaid Services: Requirement to Reduce Legionella Risk in Healthcare Facility Water Systems to Prevent Cases and Outbreaks of Legionnaires’ Disease (LD) https://www.cms.gov/Medicare/Provider-Enrollment-and-Certification/SurveyCertificationGenInfo/Policy-and-Memos-to-States-and-Regions-Items/Survey-And-Cert-Letter-17-30-.html

DEPARTMENT of VETERAN’S AFFAIRS released a guideline on the Prevention of Legionnaires’ disease in VHA Facilities. They released VHA Directive 2009-009 on February 25, 2009 on Domestic Hot Water Temperature Limits for Legionella Prevention and Scald Control. VHA Directive 1061 was released on August 13, 2014 on the Prevention of Healthcare-Associated Legionella Disease and Scald Injury from Potable Water Distributions Systems. http://www.legion.org/veteranshealthcare/216746/va-reports-legionella-prevention


Legionella Services (please contact your Account Manager for pricing)


  • Legionella Analysis, CDC Method (Includes Serogroup 1 & 2-15) Test Code 1016


  • Legionella Analysis, CDC Method (Includes Serogroup 1 & 2-15) Test Code 1017
  • Sewage Screen (E.coli/fecal coliforms, Enterococcus) Test Code 1028


  • Legionella Analysis, CDC Method (Includes Serogroup 1 & 2-15) Test Code 1063


  • Legionella Analysis, CDC Method (Includes Serogroup 1 & 2-15) Test Code 1015
  • Legionella pneumophila Serogrouping and non-pneuomphila Speciation (potable) Test Code 1515
  • Legionella pneumophila Serogrouping and non-pneuomphila Speciation (non-potable) Test Code 1516
  • Heterotrophic Plate Count Test Code 2056
  • E. coli / Total coliforms (Potable) Test Code 1010
  • Sewage Screen (E.coli/fecal coliforms, Enterococcus) Test Code 1028
  • Bacterial Count w/ Complete Genus ID Test Code 1007
  • Culture, Total Fungal Count w/Identifications Test Code 1032
  • Adenosine Triphosphate (ATP) Test Code 2015


  • Nitrifying Bacteria (BART Kit) Test Code 1070
  • Nitrifying Bacteria (BART Kit) Test Code 1071
  • Sulfate-Reducing Bacteria Test Code 1072

To learn more about Legionella testing and our related services please request information using the form here or call us at (877) 648-9150. Thank you!