Legionellosis is a group of infections caused by legionella bacteria. The bacteria can cause two types of illnesses: Legionnaires’ disease and Pontiac fever. Legionnaires’ disease is a serious illness that causes severe pneumonia. Pontiac fever causes a mild, flu-like illness without pneumonia. Legionellosis is not contagious and cannot be spread from person to person.
Toronto Public Health (TPH) continues to investigate an outbreak of Legionnaires’ disease in the southeastern area of Toronto, with 12 confirmed cases identified in late March and April that are locally clustered. The increase in confirmed cases reflects additional information received through the ongoing investigation and case follow-up. Two of the three new cases are individuals that were known to TPH and have since been confirmed as part of the outbreak.
The investigation indicates that these cases may be linked as they all occurred close together in time and location. No source has been identified, and the investigation is ongoing. Public health officials have inspected the area for potential exposures, collected samples from possible sources in proximity to the cases, and collaborated with other City divisions, local public health units, and provincial and federal partners. The risk to the public remains low.
Symptoms of Legionnaires’ disease usually start two to ten days after exposure but can be up to 19 days after exposure. Symptoms of Pontiac fever usually start 24 to 48 hours after exposure but can range anywhere from five to 72 hours.
Legionnaires’ disease is a serious form of pneumonia. Pontiac fever is a milder illness without pneumonia. Symptoms may include:
Legionellosis is not contagious and cannot be spread from person to person.
Legionella bacteria are found naturally in water sources and soil and can be found in poorly maintained human-made water systems like cooling towers, hot tubs, sprinkler systems, humidifiers, hot water tanks, whirlpools, spas, and decorative fountains. People can get infected by breathing in small droplets of water in the air containing the bacteria.
You cannot become infected by drinking water containing legionella bacteria.
People most at risk of Legionnaires’ disease include:
Legionnaires’ disease is more common in men than women and is rare in children and young adults.
Legionellosis is diagnosed based on symptoms and diagnostic testing that can show whether you have been recently infected with Legionella bacteria. The most common test is the urinary antigen test, which detects Legionella bacteria in urine. Lower respiratory tract fluids can also be tested for Legionella bacteria.
Most cases of Legionnaires’ disease can be treated successfully with antibiotics. People with Pontiac fever generally recover on their own within a week.
The best way to protect yourself from legionellosis is to maintain water systems in and around the home to prevent the growth of legionella.
Call Toronto Public Health at 416-338-7600 (TTY at 416-392-0658) or speak to your health care provider. You can also call 811 to connect to a registered nurse day or night for free, secure and confidential health advice.