City of Hamilton’s Public Health Services is investigating several cases of Legionnaires’ disease. Legionnaires’ disease is a type of pneumonia that is caused by legionella, a bacterium found primarily in warm water environments.

Legionella pneumophila bacteria/CDC
Legionella pneumophila bacteria/CDC

Public Health has received reports of six cases since the beginning of July which is at the high end of the expected number of cases for this time period. The investigation is focused in the east end of the city. The investigation is determining possible sources of exposure for each case. While the investigation is ongoing no common source is suspected to be the cause of these infections. When looking for sources of exposure, items of concern include air conditioning systems, water cooling towers, humidifiers and hot tubs and spas.

“Hamilton is seeing increased legionella activity. While Legionella is ubiquitous in the environment it is often a summertime phenomenon – especially during warm, humid summers. The risk to the broader community is low. Those at highest risk for infection are aged 50 or older and people with weakened immune systems. As we continue our investigation to seek out potential sources, we remind residents to ensure all mist-producing devices, such as showerheads, hot tubs, whirlpools and humidifiers are regularly maintained.” – Dr. Elizabeth Richardson, Medical Officer of Health 

As a preventive measure, Public Health Services has communicated with all cooling tower owners and operators reminding them of the importance of maintaining their cooling tower(s) so as to minimize legionella growth. Local health care providers have also been made aware of the local legionella activity so that they can take any appropriate action with their patients.