With local cases of Legionnaires’ disease continuing to rise, public health officials say they are actively working to reduce the risk of infection and determine the source of Legionella bacteria that caused the Orillia outbreak.
There are now a total of 27 confirmed cases, up from 19 on Oct. 7, with 10 patients currently hospitalized and two in intensive care.
People can develop Legionnaires’ disease when they inhale aerosolized water droplets containing the bacteria.
Public health officials have pointed to the City of Orillia’s 11 cooling towers as a likely source of the outbreak. Cooling towers can harbour the bacteria and spread it through releasing aerosols into the environment.
“Given that we think that it is one of the 11 cooling towers in Orillia, we've asked them to either be shut down or cleaned and disinfected,” said the region's associate medical officer of health, Dr. Colin Lee. “Six have been shut down, and the remaining five are in the process of being cleaned and disinfected.
“The usual approach would be to try to use where the cases are, where the cooling towers are, and try to make some predictions on where it might be,” he added. “We've taken the approach of we're just going to make sure the risk is decreased as much as possible.”
Given the size and spread of the outbreak, Lee said the health unit is fairly confident it originated in a cooling tower.
“If the hypothesis is true, then moving forward from the end of next week, or maybe even earlier … we shouldn't be seeing any more cases,” he said. “By doing this, even though we don't know exactly which tower it is, we're decreasing the risk to the public as much and as quickly as possible.”
Lee said the health unit has taken a number of samples from the city’s cooling towers, as well as several from infected patients. He's hoping to have results next week.
Determining the source of infection is complex, however, Lee said.
“Testing for Legionella in the environmental samples is not like when you go for a COVID test, where it's just positive or negative. It's not easy to interpret,” he said.
“It's complex to interpret… because if you went to test a number of cooling towers where there's no human disease, you're liable to find some Legionella, and the question is, is it enough to cause disease?” said Lee. “Sometimes you might find a little bit of Legionella in a cooling tower, but it's not the same species as the one in the sputum, and therefore can't really say that caused it.”
Lee noted that, globally, the source of Legionella infections often goes undetermined.
He said the health unit will be working closely with the community to reduce the risk of its spread.
“The most important thing for these cooling towers is really good preventive maintenance, and certainly we will be looking into each of these cooling towers and make sure that they do have (that)… which means periodic inspection, testing, ensuring there's enough biocide to kill germs, that kind of thing,” Lee said.” As for people who are in Orillia right now, I would say that moving forward the risk, I think, will be tremendously decreased.”
Lee said that, historically, Simcoe-Muskoka would see a handful of cases per year, but numbers have increased annually since around 2018.
Asked why the number of annual cases is trending upwards, Lee suggested climate change plays a contributing role.
“This is actually quite a big increase, as you can see,” he said. “We think climate change has something to do with it because we're getting more hot days than usual, and… you're going to (need) either more cooling towers or cooling towers to be functioning longer.
“As it's also hotter, it gives a greater chance for the Legionella to thrive because Legionella, in water, thrives at the temperatures between 20 and 45 degrees Celsius," Lee added.
People cannot get Legionnaires’ disease by drinking water and it cannot be passed from person to person. Most people exposed to the bacteria do not become ill.
Legionnaires’ disease is a type of pneumonia caused by the Legionella bacteria. People over the age of 50, smokers, or those with certain medical conditions, including weakened immune systems, chronic lung disease or other chronic health conditions, are at increased risk for Legionnaires’ disease.
Legionnaires’ disease can be treated with antibiotics and most cases resolve without long-term effects.
