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Middlesex-London Health Unit

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Health Unit Advises How to Prevent the Spread of Legionella Bacteria

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London, ON – The Middlesex-London Health Unit is advising property managers of apartment complexes, community centres, institutional buildings, etc. of an increase in the number of Legionella related illnesses in Ontario over the summer months, and how to prevent the transmission of Legionella bacteria.

Legionella bacteria can lead to serious illness. 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.

To prevent the spread of Legionella bacteria, the Health Unit recommends that property managers:

  • 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 such as nearby construction and high dust occurrences with cooling towers.

In the ten-year period between 2002 and 2011, there was an annual average of one Legionella case reported in the City of London and the County of Middlesex.

For more information on Legionellosis and how to prevent the occurrence of Legionella within your community, please refer to the following resources:

  • Cooling Technology Institute. (2008, July). Legionellosis guideline: Best practices for control of legionella. Retrieved from
  • Canadian Centre for Occupational Health and Safety. (2006, April). Legionnaire's Disease. Retrieved from
  • American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (2000). Minimizing the risk of Legionellosis associated with building water systems (ASHRAE Guideline 12-2000). Atlanta, GA: Author.

Media Contact:
Alex Tyml, Online Communications Coordinator, Middlesex-London Health Unit, 519-663-5317 ext. 2560 or 226-236-1941 (cell.)

Iqbal Kalsi, Manager of Environmental Health, Middlesex-London Health Unit

Tags: news, media release, legionella