With no new confirmed cases in the past nine days, the Simcoe Muskoka District Health Unit says the legionnaires’ disease outbreak in Orillia is likely winding down.
To date, there has been one death and 35 confirmed cases over the course of the outbreak, with 29 patients requiring hospitalization.
Currently, three patients remain hospitalized, with one in the ICU, officials say.
Dr. Colin Lee, the region’s associate medical officer of health, said it’s a “great sign” no cases have been reported in nine days.
Orillia experienced a torrent of cases over the previous several weeks, in an outbreak that eclipsed the case counts of previous outbreaks in the region.
“That would suggest that what was causing the very quick increase in cases, in a short period of time, is no longer an issue, or at least there’s an increasing chance with each day,” he said. “We're hoping that by the end of next week we may be able to declare the outbreak over.”
“The risk of actually getting Legionella at this time, I think, is very, very low.”
The health unit suspects the bulk of the infections occurred in mid-September, and said the source of the outbreak is likely a local cooling tower - a rooftop system used in large buildings for heating and air conditioning.
Seven cooling towers have closed either in response to the outbreak or prior due to decreased cooling needs heading into the fall, Lee said Wednesday.
“We've looked into … 12 either currently active or previously active cooling towers,” Lee said. “We've either tested all of them, or asked them to shut down, or asked them to clean and disinfect, or a combination of those things.
“The cooling towers that are currently in operation … have tested negative, certainly, in the last week, so they are safe in our estimation.”
The health unit is waiting for additional test results, which should arrive by the end of next week, although Lee stressed it is unlikely a source of infection will be determined.
Lee said that part of determining an outbreak’s source is finding a genetic match between a patient’s sputum and a Legionalla culture from the community.
Part of the difficulty in determining a source is that patients are most easily diagnosed through a urine test, Lee said. When a sputum sample is taken – which patients do not always provide – they have often been taking antibiotics for several days, which can impact the viability of the sample.
Lee has previously noted that, globally, the source of Legionella outbreaks often go undetermined.
