Q&A: Legionella and Legionellosis (Legionnaires’ Disease)


Q&A: Legionnella and Legionellosis (Legionnaires’ Disease) Information When Living in a Multi-Unit Building

1. What is ‘Legionnaires’ disease’?

‘Legionnaires’ disease’ is a disease caused by the legionella bacteria that can lead to pneumonia. There is also a milder form of Legionnaires’ disease: legionella fever, sometimes called Pontiac Fever. ‘Legionnaires’ disease’ does not occur often. The disease is not new. It was identified in 1976, when a pneumonia epidemic occurred during a convention for war veterans of the American Legion in Philadelphia (USA). In Canada, the average number of reported cases of Legionnaires’ disease is generally less than 100 per year.

2. Where does the legionella bacteria occur?

The bacteria causing the disease can be found in very small quantities in the ground, and in water and tap water. The legionella bacteria becomes a problem when it is able to multiply, e.g. in water with a temperature between 20 Celsius and 50 Celsius that is stagnant for a long period of time. A strong flow can prevent the growth of the bacteria, but if this flow is not constant throughout an entire hot water system, water could become stagnant in certain spots (so-called dead corners), where further growth could occur, creating a risk.

3. What are the symptoms of Legionnaires’ disease?

The period between being infected with the bacteria and the first symptoms of the disease (the incubation period) is approximately two to fourteen days. The symptoms of Legionnaires’ disease may include: fever, chills, dry cough, muscle aches, headache, loss of appetite, diarrhea, and pneumonia. The disease can have serious consequences, but can be treated effectively by administration of antibiotics.

4. What is the treatment for Legionnaires’ disease (the ‘severe’ form)?

This disease can be treated effectively. Recovery is possible if the antibiotics are administered promptly; these antibiotics can be prescribed by any doctor and hospitalization is often required. It may take several weeks before the patient recovers. The sooner the treatment is started, the better. If Legionnaires’ disease is not treated correctly or promptly it can be fatal.

5. How is infection transmitted?

Infection occurs through the lungs. It is assumed that the infection is transferred by inhaling the bacteria in droplets of water suspended in the air (misting). The disease is not contagious; it cannot be transferred from one person to another. Pets cannot become infected with Legionella.


6. Is it still safe for me to take a shower?

If you take showers, take a bath instead. While you’re filling the tub, stay outside the bathroom and keep the bathroom door closed.

7. Is there a risk of being infected via the tap; for example while doing the dishes?

There is no risk when doing the dishes.

8. Is there a risk of infection when using a coffee-maker or steam iron?

There is no risk. Coffee-makers and steam irons work with temperatures considerably higher than 60 Celsius, which make it impossible for the bacteria to grow.

9. Is it safe to use a plant spray if it has been on the windowsill (in the sun) for some time?

We strongly recommend that you drain the water from the plant spray after use and refill it before using it again.

10. What about air conditioning devices or humidifiers in my home?

If you have an in-unit air conditioning device or humidifier, turn it off.

11. Could the air conditioning in my car cause a problem?

Since these systems do not create a mist, there is no risk from the air conditioning in cars.

12. What can I do personally to prevent infection with the legionella bacteria?

You can take the following precautions:

  • If you have an in-unit air conditioning device or humidifier, turn it off.
  • If you are using respiratory devices, be sure they are cleaned according to manufacturer’s

    instructions. To be safe, use boiled and cooled water to clean.

  • If you take showers, take a bath instead. While you’re filling the tub, stay outside the bathroom and

    keep the bathroom door closed.

  • After being away for a few weeks you can clean the water supply by flushing the shower with hot

    water only, while leaving the door open for ventilation. This way the water supply will be cleaned.

If you have a whirlpool bath in the correct manner by cleaning the pumps and filters. Cleaning the

bath properly with household cleaning products, such as chlorine, is a standard measure, and would also be advisable in this case.

Adapted, September 3, 2015 from the following References:

Legionnaires’ Disease Foundation, Netherlands (2015). 42 Questions on Legionnaires’ Disease. Retrieved from http://www.legionnairesdisease.nl/about- legionnaires%E2%80%99-disease/42-questions-on-legionnaires%E2%80%99-disease

Nova Scotia (2015). CDC Manual: Legionellosis. Retrieved from http://novascotia.ca/dhw/cdpc/cdc/documents/Legionellosis.pdf
Nova Scotia (2015). Legionellosis General Information. Retrieved from http://novascotia.ca/dhw/cdpc/cdc/documents/Legionellosis-General-Inform... Public Health Agency of Canada (2015). Legionella. Retrieved from http://www.phac-aspc.gc.ca/id-mi/legionella-eng.php

US Department of Labor (2015). Occupational Safety and Health Administration Technical Manual: Chapter 7 Legionnaires’ Disease. Retrieved from



Public Health

7 Mellor Ave, Unit 5 Dartmouth, NS B3B 0E8 Tel (902) 481-5800