No single source for 9 Moncton legionnaires' disease cases
Public Health found several smaller 'clusters' of cases in outbreak that was declared over in October
Public Health says testing determined there was no single source for nine legionnaires' disease cases in the Moncton region this year as it announced the end of its investigation.
In the first update in more than two months, Dr. Yves Léger, regional medical officer of health, laid out a complex explanation of the cases.
"I think we can clearly say that we were not definitely dealing with one outbreak per se, which usually means an increase in cases that are linked to one common source," Léger told reporters Wednesday in a news conference. "In fact, there were a few distinct clusters or grouping of cases."
Léger said there are three separate groups within those nine cases based on laboratory testing, but he left open the possibility none within those three groups are linked to common sources.
The outbreak investigation was declared over in late October, though this wasn't disclosed until Wednesday. The total number of cases is one higher than what had been previously made public in mid-September.
Léger had declared an outbreak Aug. 6 when Public Health was aware of six people ill with legionnaires' disease, a severe form of pneumonia that's fatal in about 10 to 15 per cent of cases. Seven of the nine were hospitalized, one person died.
Legionnaires' disease is caused by inhaling legionella bacteria, which is found in many natural waterways. It's also found in man-made systems like decorative fountains, spas and cooling towers.
Léger told reporters he declared an outbreak because it was unusual to see so many cases reported in such a short period, raising suspicions they were dealing with an outbreak similar to one traced to cooling towers in Moncton in 2019 that infected 16 people.
Cooling towers have often been determined to be the source of outbreaks. The mechanical equipment is part of a centralized air-cooling system for a variety of types of buildings. Bacteria can grow and spread into the community on mist carried from the towers by the wind. The illness doesn't spread person-to-person.
However, Léger said a series of subsequent laboratory tests of samples from patients and from cooling towers in the region led Public Health to determine the cases weren't all linked to one source as they were in 2019.
Instead, he said they may be what's known as sporadic cases that occur but aren't part of an outbreak. In some of those cases, a specific source can't be found. An average of five cases were reported per year across New Brunswick, according to a 2018 report.
The first of the nine cases was reported to Public Health on July 26, while the last case was reported Sept. 15. The people infected ranged from their mid-20s to early 90s.
Public Health tested at 69 cooling towers at 42 locations in the Moncton region.
Four had elevated bacteria levels and were cleaned and later tested, but none had high enough bacteria levels to require an immediate shutdown. He didn't name the four locations with towers that had elevated bacteria levels.
I certainly don't have any reason to believe that there's any ongoing risk in the community from cooling towers. - Dr. Yves Léger
Léger said lab testing showed a mix of different strains of legionella bacteria in those cooling towers.
Testing linked one patient's infection to bacteria found in cooling towers, but that same strain was found in two separate cooling towers located three kilometres apart, making it hard to determine how the person was infected.
Léger, asked whether there's a risk to people in Moncton given no single source was determined, said the bacteria is present everywhere in the environment.
He said people can reduce their risk by making sure hot-water systems such as hot tubs are properly maintained.
"In terms of looking at the outcome of our investigation here in our nine cases, I certainly don't have any reason to believe that there's any ongoing risk in the community from cooling towers," he said, noting they tested every cooling tower they are aware of in the region.
He reiterated that recommendations he issued following the 2019 outbreak for a cooling tower registry and associated maintenance rules are still important to implement.
Dorothy Shephard, the province's health minister, told CBC in September she expects legislation to implement those recommendations will be introduced next year.
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