Good evening all:

Toronto Public Health has just announced that the cause of the 7 Oaks outbreak is Legionnaires disease. This bacteria was first discovered at a hotel in Philadelphia in 1976 and is now recognized as a common cause of community and hospital-acquired pneumonia. This explains many things including the higher than normal death rate, the described symptoms, and the fact that patients appeared to be improving on antibiotics. 

Legionnaires disease can sometimes be difficult to diagnose which explains why it took a week to discover it was the cause. The bacteria that causes Legionnaires disease is commonly found in water and soil, so Toronto Public Health is now investigating where it might have come from. It is not transmissible person to person so this news should allay everybody's fears that an outbreak is spreading in the city.

I expect that media interest in this outbreak will vanish now that we know the cause. Hopefully next time we have an outbreak like this, things will unfold in a calmer fashion!


Michael Gardam MSc, MD, CM, MSc, FRCPC 
Director, Infection Prevention and Control 
Medical Director, Tuberculosis Clinic 
University Health Network​

Back to Top