Legionellosis

What is legionellosis?

Legionellosis is a disease caused by Legionella bacteria. Two different diseases make up legionellosis, Legionnaires' disease and Pontiac fever. Legionnaires' disease causes a serious type of pneumonia, a lung disease. Pontiac fever is a milder infection than Legionnaires' disease.

How do I get Legionnaires' disease?

Legionella bacteria live naturally in freshwater environments, like lakes and streams. In these natural environments, they are not dangerous to people. They can cause health problems in people when they grow in human-made water systems. These can include:

• Showerheads and sink faucets
• Hot tubs
• Hot water tanks and heaters
• Windshield wiper fluid tank of a vehicle (Especially if filled with water. Always use windshield washer fluid.)
• Cooling towers (part of a large air conditioning system)
• Decorative fountains and water features
• Large, complex plumbing systems (like in large buildings)

Legionella bacteria spread in tiny water drops through the air. People can get Legionnaires' disease or Pontiac fever when they breathe in these water drops. The water drops in mist (aerosolized water) can get down into the lungs.

In general, people do not spread the bacteria to other people. This may be possible under rare circumstances.

Who is at greater risk for Legionnaires' disease?

Most healthy people exposed to Legionella do not get sick. People at greater risk of getting sick are:

• People 50 years of age or older
• People who smoke now or used to smoke
• People with a chronic lung disease (like chronic obstructive pulmonary disease or emphysema)
• People with weak immune systems or who take drugs that weaken the immune system (like after a transplant operation or chemotherapy)
• People with cancer
• People with underlying illnesses like diabetes, kidney failure, or liver failure

What should I do if I think I have Legionnaires' disease?

Talk to a health care provider if you think you might have Legionnaires' disease. Be sure to mention if you spent any nights away from home in the last 14 days.

Symptoms

Symptoms of Legionnaires' disease begin 2-14 days after exposure. Common symptoms of Legionnaires' disease include:

• Cough
• Shortness of breath or difficulty breathing
• Fever or Chills
• Muscle or body aches
• Headache
• Nausea or vomiting
• Diarrhea
• Confusion

Pontiac fever is a milder infection than Legionnaires' disease. The most common symptoms are fever and muscle aches. Symptoms begin between a few hours to 3 days after exposure. Symptoms usually last less than a week. Pontiac fever does not usually include pneumonia.

Preventing Legionellosis at Home

Hot Tubs

Legionella grows best in warm water, like the water temperatures in hot tubs. The warm temperatures in hot tubs can make it hard to keep disinfectants at the levels needed to kill germs like Legionella. [Learn more](https://www.cdc.gov/control-legionella/php/toolkit/hot-tub-module.html?CDC_AAref_Val=https://www.cdc.gov/legionella/wmp/control-toolkit/hot-tubs.html) about how to clean your hot tub properly.

Hot Tub Maintenance

To prevent the growth and spread of bacteria like Legionella in your hot tub, perform these activities regularly:

• Check disinfectant and pH levels.
• Check levels more often when the hot tub is being used by a lot of people.
• Test these levels:
• Chlorine: Free chlorine level should be 3-10 parts per million.
• Bromine: Bromine level should be 4-8 parts per million.
• pH: pH should be 7.2-7.8.
• Remove slime or biofilm by scrubbing and cleaning.
• Replace the hot tub water filter according to manufacturer's recommendations.
• Replace the hot tub water.

Read more about recommended test kits and proper disinfection.

Download the checklist (PDF).

Disinfecting a Hot Tub

If there is an outbreak or illness suspected, follow these cleaning guidelines:

• Remove the hot tub from use.
• Drain the hot tub after collection of samples per public health instructions.
• Scrub and clean all surfaces, including skimming devices and wires. Use water with a minimum free chlorine concentration of 5 parts per million.
• Rinse all hot tub surfaces with fresh potable water and drain as needed.
• Replace filters or filter media (if applicable).
• Repair parts as needed.
• Refill the hot tub with fresh potable water.
• Increase chlorine in the water (hyperchlorinate) to 20 parts per million free chlorine.
• Circulate hyperchlorinated water with jets off for 1 hour.
• Circulate hyperchlorinated water with jets on for 9 additional hours.
• Maintain a minimum free chlorine residual of 20 parts per million for a total of 10 hours.
• Flush the entire system with fresh potable water and refill.
• Return the hot tub to the routine disinfectant residual level.
• Resume service. Coordinate with Maine CDC as necessary.

Download the checklist (PDF).

CPAP and Humidifier Users

Humidifiers and respiratory equipment can grow Legionella bacteria. The bacteria can transfer to your lungs through the fine mist of water. Regularly clean your equipment per the manufacturer's instructions to keep it free of bacteria. Fill your humidifier with distilled water or water that you boiled for one minute and then let cool down. This protects you from any bacteria that may be in your plumbing system.

CPAP and Humidifier Maintenance

Perform these activities regularly:

• Clean your equipment per the manufacturer's instructions to keep it free of bacteria.
• Empty and clean tanks daily. Allow to dry between uses.
• Fill your tank with distilled water or water that you boiled for one minute and then let cool down.

Download the checklist (PDF).

Hot Water Heater Maintenance

If you have access to or control of your water heater, follow this guidance to maintain your water heater. If you live in a care facility or apartment building, your property manager or landlord handles the hot water system. If you have concerns about Legionella exposure in your building, check with them. Ask about their water quality management plan to reduce the risk of Legionella growth.

Water Heater Maintenance

Take these steps to maintain your water heater:

• Set the water heater temperature.
• If your water heater has a tank, set your heater to 140°F to reduce the growth of Legionella.
• To better reduce Legionella growth, the temperature leaving the faucet should be at or above 120°F.
• This temperature is very hot and can scald or burn skin.
• To help prevent scalding, you can install point-of-use mixing to control the water temperature at the showerhead or faucet. Contact a plumber if you do not know how to do this.
• Flush the water heater tank when needed.
• It isn't always possible to drain your water heater tank.
• If possible, emptying and refilling (flushing) the water tank is a good practice. You can hire a plumber to do this for you.
• Completely flush (empty and refill) your water heater:
• When you return after a week-long or more vacation.
• Before you move into a home.
• After plumbing work.
• If you have discolored hot water.

Steps to flush your water heater tank:

• Turn off the gas or electricity to the water heater.
• Open a hot water faucet in the home and run the water for about 10 minutes to reduce the water temperature in the tank.
• Attach a garden hose to the existing drain valve and route it to a floor drain.
• With the cold water valve open to drain the tank, open the drain valve. Please use caution, as sediment can build up within the water tank and clog the drain line or valve.
• Follow the manufacturer's procedure for restarting your hot water heater.

Download the checklist (PDF).

Shower Head Cleaning

Legionella can grow in your shower heads and faucets. Clean shower heads and faucets regularly to lower the growth of Legionella bacteria. Follow this guidance for cleaning your showerhead.

Clean Your Shower Head to Prevent Legionella Bacteria

Clean your shower head regularly:

• Take apart the shower head.
• Remove any limescale and other debris.
• Place the shower head fixture in a bucket filled with vinegar or chlorine bleach.
• Let the shower head soak for a few minutes to remove any deposits.
• Rinse the shower head with fresh water and put back together.

Helpful housekeeping tips:

• Use your shower daily to prevent water from becoming stagnant.
• Run your faucets and showers for at least 3 minutes when they have been out of use for more than a week.

Download the checklist (PDF).

Preventing Legionnaires' Disease for Building Owners and Managers

Preventing Legionnaires' Disease in Your Building

Understand how Legionella bacteria grow and spread in buildings.

Different factors play a role in a Legionella problem in your building. These include:

• Construction
• Water main breaks
• Changes in municipal water quality
• Biofilms
• Scale and sediment
• Water temperature fluctuations
• pH fluctuations
• Inadequate levels of disinfectant
• Changes in water pressure
• Water stagnation

Learn more about how these factors help Legionella grow and ways you can prevent it here.

Find out if you need a water management program for your building or certain devices in your building.

In some settings, like large buildings with complex water systems, you need a water management plan for the entire building. In smaller buildings with simple water systems, you may only need a plan for devices that aerosolize water.

Use this worksheet to figure out if you need to develop a water management plan.

Create your Legionella Water Management Program.

Use this toolkit to develop your water management plan.

Take this training course on creating a water management program to reduce the risk for Legionnaires' disease. This training is ideal for the complete range of professions involved in water management programs. This includes:

• Building managers
• Maintenance/engineering staff
• Safety officers
• Equipment and water treatment suppliers
• Consultants
• Public health professionals
  • Consider working with a Legionella consultant to help build an effective water management plan.
  • Factors to consider when creating your water management program:
• Principles of effective water management:
  • Maintaining water temperatures outside the ideal range for Legionella growth.
  • Preventing water stagnation.
  • Ensuring adequate disinfection.
  • Maintaining devices to prevent sediment, scale, corrosion, and biofilm. All of these provide a habitat and nutrients for Legionella growth.
• Seven key elements of a Legionella water management program are:
  • Establish a water management team.
  • Describe the building water system using text and flow diagrams.
  • Identify areas where Legionella could grow and spread.
  • Decide where control measures should be applied and how to monitor them.
  • Establish ways to intervene when control limits are not met.
  • Make sure the program is running as designed and is effective.
  • Document and communicate all activities.

If your building already has a water management program, consider using the CSTE Water Management Program Evaluation (PDF) to ensure your water management program is effective at preventing and controlling Legionella.

Regularly monitor water in your building.

Consider routine testing for Legionella.

Responding to Legionella detection in a building

There is no known safe level or type of Legionella in building water systems. If you detected Legionella in your building:

• Use this Performance Indicator Interpretation to determine how well-controlled Legionella in your building is based on your positive samples.
• You only need to report a Legionella detection in a building to Maine CDC if there is a known associated case in a person. However, Maine CDC provides limited consultation services for any Legionella detection at 1-800-821-5821.

If your building samples show that Legionella is not well-controlled, take these steps:

• Review your sample collection, sample handling, and testing for potential errors.
• Confirm that system equipment is in good working order and functioning as intended.
• Consider messaging to key audiences.
• You may want to issue messaging depending on your test results and the population served by your building. Maine CDC can help you determine what type of messaging to use. Call Maine CDC's 24-Hour Disease Reporting Hotline at 1-800-821-5821.
• Review your records to confirm that the water management plan was implemented as designed.
• Review assumptions about operating conditions. This includes physical and chemical characteristics of incoming water.
• Re-evaluate fundamental aspects of the water management plan. Include analysis of hazardous conditions, cleaning, maintenance procedures, chemical treatment, and other aspects that could affect Legionella testing.
• If your facility does not have a water management program, complete an Environmental Assessment (PDF). This will help you understand your facility's water systems and devices to minimize the risk of Legionnaires' disease. Use the Environmental Assessment Marking Guide (PDF) to walk you through the assessment.
• Adjust your water management plan to address any deficiencies identified during your evaluation.
• Consider if remedial treatment is needed only after completing the steps above.
• If you perform remedial treatment, wait at least 48 hours after the system returns to normal operating conditions. Then retest a set of representative samples to confirm the effectiveness of the response.
• Consider working with a Legionella consultant. They will help with remediation, environmental assessments, and developing your water management plan. Consider these things when hiring a consultant.

Responding to an outbreak in people associated with a building

You may have an outbreak of Legionella associated with your building if:

• 2 or more people have legionellosis within 12 months of each other, AND
• They lived in, worked in, or visited the same building during their incubation period.

If you think you have a Legionnaires' disease outbreak associated with your building:

• Report the outbreak to Maine CDC at 1-800-821-5821.
• Maine CDC will work with you to take steps to stop the spread of Legionella bacteria and protect the people your building serves.

Water Management for Health Care Facilities

• In June 2017, the Centers for Medicare & Medicaid Services (CMS) released a survey and certification memo (PDF). This stated that health care facilities should develop and adhere to ASHRAE-compliant water management programs. These water management programs help reduce the risk for Legionella and other pathogens in their water systems.
• A comprehensive water management program can help control other water-related healthcare-associated infections. Monitor water management programs for their efficacy in reducing risk for a variety of pathogens.
• According to the U.S. CDC Healthcare Infection Control Practices Advisory Committee (HICPAC), health care facilities have two options for confirming that their water management program is working as intended. (Refer to Guidelines for Preventing Health Care Associated Pneumonia.)

These options are:

1. Performing environmental sampling for Legionella bacteria.
2. Performing active clinical surveillance for infections due to Legionella.

Use the Legionella Environmental Assessment Form (PDF) to guide environmental sampling plans and develop a water management program.

Legionnaire's Disease Prevention for Hotels and Vacation Rentals

Nearly 15% of Legionnaires' disease patients were travel-associated. This means they reported staying overnight at hotels, private homes, or vacation rental properties.

Outbreaks at hotels and resorts may interrupt services. This can diminish the guest experience and lead to considerable financial and reputational costs.

Legionella can grow and spread in many areas of hotels and resorts. Areas of particular concern include cooling towers, showers, unoccupied floors or rooms, hot tubs, and decorative fountains. Any water supply interruptions, such as nearby construction, can make Legionella growth more likely. The problems that lead to Legionnaires' disease are preventable through water management programs.

For more information on prevention Legionella growth in travel accommodations, visit:

• Preventing Legionnaires' Disease for Vacation Rental Owners
• Preventing Legionnaires' Disease for Hotel Owners and Managers

Legionnaires' Disease Information for Health Care Providers

Clinical features of Legionnaires' disease include:

• Cough
• Fever
• Radiographic pneumonia

Signs and symptoms of Legionnaires' disease are similar to pneumonia caused by other pathogens. The only way to tell if a pneumonia patient has Legionnaires' disease is by getting a specific diagnostic test. Indications that warrant testing include:

• Patients who have failed outpatient antibiotic treatment for community-acquired pneumonia.
• Patients with severe pneumonia, in particular those requiring intensive care.
• Immunocompromised patients with pneumonia.
• Patients with a travel history (patients who traveled away from their home overnight within 14 days before symptom onset).
• Hospitalized patients with healthcare-associated pneumonia (pneumonia with onset ≥48 hours after admission) at risk for Legionnaires' disease.
• Patients with an overnight stay in a health care facility within 14 days before symptom onset.
• Patients with an epidemiologic link to a setting with a confirmed source of Legionella or that has been associated with at least one laboratory-confirmed case of Legionnaires' disease.

Diagnostic Testing

Preferred diagnostic tests for Legionnaires' disease:

• Culture of lower respiratory secretions (sputum, bronchoalveolar lavage, etc.) on selective media
• Legionella urinary antigen test
• Best practice is to obtain both concurrently

Culture:

Isolation of Legionella can come from lower respiratory secretions, lung tissue, pleural fluid, or a normally sterile site. Culturing specimens can detect Legionella species and serogroups that the urinary antigen test does not.

• Comparing clinical isolates obtained from culture and environmental isolates using serologic and molecular techniques can help identify the source in Legionnaires' disease outbreak investigations. Send all Legionella isolates obtained from culture to Maine Health and Environmental Testing Laboratory (HETL) for this purpose.

Urinary Antigen Test:

The urinary antigen test (UAT) is the most commonly used laboratory test for diagnosis of Legionnaires' disease, which detects a molecule of the Legionella bacterium in the urine. UAT detects Legionella pneumophila serogroup 1, the most common cause of Legionnaires' disease. However, all species and serogroups of Legionella are potentially pathogenic, so a patient with a negative urinary antigen result could have Legionnaires' disease caused by other Legionella species or serogroups, which is why using culture and UAT in combination is recommended.

Specimens should be obtained prior to antibiotic administration, but antibiotic treatment should not be delayed to facilitate this process.

Treatment

If your patient has Legionnaires' disease:

• See the most recent guidelines for treatment of community-acquired pneumonia and hospital-acquired pneumonia.
• Macrolides and respiratory fluoroquinolones are currently the preferred agents for treating Legionnaires' disease.
• If your patient has Pontiac Fever, antibiotic treatment should not be prescribed. It is a self-limiting illness that does not benefit from antibiotic treatment. Patients usually recover within 1 week.
• While it is preferred that you obtain diagnostic testing before antibiotic administration, antibiotic treatment should not be delayed to facilitate this process.

Legionnaires' Disease Data

Legionellosis Surveillance Reports 2010 (PDF) | 2011 (PDF) | 2012 (PDF) | 2013 (PDF) | 2014 (PDF) | 2015 (PDF) | 2018 (PDF) | 2019 (PDF)

Resources

• Legionellosis Factsheet (PDF)
• Hot Tub Maintenance Checklist (PDF)
• Disinfecting a Hot Tub Checklist (PDF)
• Hot Water Heater Checklist (PDF)
• Maintaining Humidifiers and CPAP Machines Checklist (PDF)
• Cleaning Shower Heads Checklist (PDF)