Dear Apartment/Condo Managers and Mall Managers,

Over the summer months, there has been an increase in the number of Legionella-related illnesses in Ontario.  This trend has been reflected in Waterloo Region. At the request of Ontario’s Chief Medical Officer of Health, we are writing you to provide you with information on how you can help prevent Legionella bacteria’s transmission through the maintenance of water systems (including cooling towers).

Legionella is a bacteria found naturally in the environment that can lead to lung infection and serious illness. People usually acquire the illness by breathing in contaminated water droplets or mist from aerosol-producing devices. Thus, improperly maintained water systems such as atmospheric cooling towers, hot water systems and showers, and spas such as hydro-massage tubs may contribute to the spread of Legionella bacteria.

Regular maintenance in accordance with industry standards can prevent outbreaks. We thus recommend that you:

  1. Follow this general information with respect to watery system maintenance, including cooling towers:

·         Follow equipment manufacturer maintenance instructions with regard to the operation of atmospheric cooling towers, hot water systems, and hydro-massage tubs

·         Use precaution when shutting down to ensure safeguards are in place

·         Ensure proper cleaning of the apparatus prior to re-start

·         Respond to adverse situations such as changes in the functioning of the apparatus and external influences (e.g., nearby construction and high dust occurrences  with cooling towers)

  1. Follow these resources’ additional guidance on how to prevent the spread of Legionella bacteria:

·         The Cooling Technology Institute’s Legionellosis Guidelines: Best Practices for Control of Legionella (

·         ASHRAE Guideline 12-2000: Minimizing the Risk of Legionellosis Associated with Building Water Systems (

Please click here for more information on Legionnaire’s disease. If you have any questions about this letter, you may contact Brenda Miller, Manager of Infection Control at Region of Waterloo Public Health (, 519-883-2379). We appreciate your cooperation in keeping Ontarians safe – safety is a partnership involving many people and we hope that we can count on your assistance in the prevention of Legionella outbreaks.


Dr. Hsiu-Li Wang

Associate Medical Officer of Health, Region of Waterloo Public Health