Floor swabs at LTC homes early predictor of COVID outbreaks, study finds
Tool could help prevent future outbreaks or make them less harmful, say researchers
After swabbing the floors of several Ontario long-term care homes for more than a year, scientists say sampling floors for the COVID-19 virus can help detect an outbreak days before it happens.
"It's exciting because up until now, we really haven't had a great way of being able to predict when an outbreak might happen within a long-term care home," said Mike Fralick, a clinician scientist at Mount Sinai Hospital in Toronto and the lead author of the study published in February in NEJM (New England Journal of Medicine) Evidence.
Long-term care (LTC) homes across the country were devastated by the pandemic and outbreaks continue to happen in Ottawa facilities.
According to Ottawa Public Health, outbreaks at the city's long-term care homes were the deadliest among its tracked institutional settings, with a total of 397 patient and staff deaths reported since 2020.
"We've seen what has happened in long-term care homes," said Fralick.
"Our data suggests that this approach could help to prevent outbreaks going forward and at the very least, hopefully mitigate not only the size but also the scope of these outbreaks."
How it works
Researchers partnered with 10 LTC homes — five in Ottawa, three in Toronto and two in Sault Ste. Marie, Ont. — between September 2021 and November 2022.
They sampled floor surfaces weekly at several communal spots inside each facility — from dining halls to recreation rooms — and collected close to 5,000 swabs during that period.
Fralick said the floor is the best predictor because it's pretty much a "sink, which soaks up the virus."
Then at a lab at Carleton University, researchers used a reverse transcriptase PCR test — like the ones used to swab people's noses for COVID-19 — to analyze the swabs for presence of SARS-CoV-2, the virus that causes the COVID-19 illness in people.
WATCH | A scientist takes CBC reporter through the method:
An outbreak at an LTC home, as Ontario's Ministry of Health recently defines it, happens when two or more patients test positive for COVID-19 with an epidemiological link within a seven-day period, where patients reasonably got their infections within the home.
At least five days leading up to an outbreak at most of the LTC homes, researchers found more than 10 per cent of the collected swabs tested positive for SARS-CoV-2.
To put that into perspective, that's one out of every 10 swabs.
Warning bells should sound as the number climbs from one to five swabs out of 10 testing positive, Fralick said.
During an active outbreak at an LTC home, the study found more than half of the floor swabs tested positive for the COVID-19 virus.
In some homes, he said nearly 100 per cent of swabs came back positive during an outbreak, meaning there must have been a lot of sick patients in that area of the LTC home shedding the virus.
As people began to recover, researchers saw the number of COVID-positive floor swabs decline.
Fralick says there's a strong link between the levels of SARS-CoV-2 detected on the floor and a future COVID-19 outbreak.
"What's nice about it is that it's inexpensive and it's very localized," said Fralick.
"We've shown that the science is there, it's robust, and now the question is what happens when you implement this?"
What's next?
Fralick says the next step is to get more funding and implement this tool at long-term care homes as a pilot project.
"Does it indeed reduce the size of outbreaks?" he said. "We'll be comparing homes where the floors are being swabbed against long-term care homes where there's no swabs being done."
It could help us act quicker to the threat of COVID-19 outbreaks.- Natasha Milijasevic, Extendicare
Fralick said this tool could eventually help LTC homes isolate floors that may detect higher levels of COVID-19 instead of shutting down the whole facility.
That could help ensure the continuation of social activities for other residents, as well as family visits during outbreaks in areas where little COVID is found on the floors, he said.
Researchers hope to apply this same method to test for influenza viruses and RSV, said Fralick. When the next virus comes along, the goal is to add it to their "multiplex" swab that can detect all the viruses in a single swab.
Extendicare excited about new tool
Natasha Milijasevic, senior director of quality at Extendicare, said she is excited by the "promising results." Several LTC homes run by Extendicare participated in this study.
"It could help us act quicker to the threat of COVID-19 outbreaks," she said. "We can get ahead of it earlier than we ever could before."
Milijasevic said while it's too early to say how the research might be applied across the country, where there are more than 100 Extendicare homes, the organization plans to participate in Fralick's next study.
A spokesperson for Public Health Ontario (PHO), a government agency that provides scientific advice, said it provided a letter of support for this research.
"We would use the study's findings within PHO and facilitate its use within our network of stakeholders," they wrote in an email.
"While the results of this study will likely be referenced and used to inform future PHO reports and best practices, it is not within PHO's scope to implement this kind of testing in [LTC] homes.
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