Canadian researchers say floor samples can detect COVID up to a week before cases reported

Canadian researchers are “floored” by the success of a new, effective, and simple tool they’ve developed for tracking viruses ⁠— including the SARS-CoV-2 virus that causes COVID-19.

It turns out floors are like sinks that fill up with accumulated virus. Sampling them can detect COVID-19 up to a week before cases are reported, potentially preventing or containing outbreaks and helping inform infection control decisions.

Floor sampling helps track viral spread on a smaller scale where large numbers of people congregate and wastewater sampling isn’t necessarily as useful — places like hospitals, schools, long-term care homes, workplaces, and very specific areas in those buildings.

The surface environmental testing method was discovered by the Coronavirus in the Urban Built Environment (CUBE) research team, part of the national Coronavirus Variants Rapid Response Network (CoVaRR-Net). 

Through their research, CUBE team members demonstrated that floors are the most reliable surface from which to collect samples to test for the virus’ presence. 

“When a person infected with COVID-19 breathes, speaks, coughs, or sneezes, the virus travels outward in the respiratory particles, remains suspended in the air for a time and eventually falls and settles on the floor,” notes a COVaRR-NET media release.

“Swab samples taken from floors undergo PCR testing and can indicate whether and how much of the virus is present in a specific room or building.”

CUBE project director and University of Ottawa professor Dr. Rees Kassen said besides detecting the SARS-CoV-2 virus, floor sampling can also identify and track the presence of other respiratory pathogens. 

Those could include influenza, monkeypox, and respiratory syncytial virus (RSV). RSV affects young children and is largely responsible for a recent increase in emergency department visits to the IWK children’s hospital. 

“We had the idea that if we could just take a sterile swab that looks a little bit like a Q-Tip, we could probably detect the virus, pick it up off the floor, and that would give us a signal as to how many infected people were in the area,” Kassen said in an interview. 

“They might be asymptomatic but infected, so they’d be still shedding that virus onto the floor…We wanted to know where is it, how often do we pick it up, and does how often we pick it up track in any way what’s going on in known cases or in wastewater or other ways of detecting the virus.”

Turns out it did.

Floors leapt out

The team’s first study involved two large hospitals in the Ottawa area before the arrival of the Omicron variant. Kassen said while they initially went in thinking they’d detect the virus on a variety of high-touch surfaces (door handles, computer terminals, elevator buttons, etc.), a team member at the last minute suggested adding floors to the mix.

“Lo and behold, of all the different surfaces we sampled, floors leapt out as being the one where there was the strongest signal,” Kassen said.

“The signal that we got off of floors, there was a big difference when you looked at wards in the hospital that were devoted to treating COVID patients and those that were supposed to be COVID-free.”

Because there was still a high percentage of individual testing at the time, especially in hospital settings, their samples tracked what was being seen in case numbers reported by the hospitals. 

The team then branched out to a series of long-term care homes in three Ontario cities. Using a similar approach, they sampled different areas in the homes.

“We found that actually we were picking up this virus and it was allowing us to actually anticipate by often up to five to seven days a declared outbreak in the home as the homes are obliged to declare them by provincial guidelines,” Kassen said. 

“When we saw samples from the floor starting to rise, when that signal started to rise, that was an indication that something important was going on and an outbreak was impending.”

Detectable even hours after cleaning

The floor method still works well at detecting the virus even in areas that are cleaned frequently. Kassen said that’s because as soon as someone who’s infected enters a room and starts breathing, the virus begins to accumulate. His team is wrapping up another study looking at the accumulation of COVID-19 in patient rooms in a number of hospital scenarios. 

That study indicates the virus is once again detectable on the floor within hours.

“So somebody comes into the hospital, is diagnosed as having COVID, and they get put into a room that had been cleaned already and then in isolation,” Kassen said. 

“We sample over time and from different distances from the bed of the patient and the short version of the story is that the virus is almost everywhere we sample, from the patient’s bed to the door, within hours.”

Beyond alerting institutions, businesses or organizations to the likelihood of an outbreak so they can implement mitigation measures, Kassen said it could also help when it comes to more effectively managing staffing issues.

“For organizations like large businesses that might run a factory or a warehouse or anywhere where people congregate and where staffing is an issue, this would be a signal to the managers of those organizations and institutions that, you know what, we’ve got to think about what might be happening,” he said.

“This gives a few days heads-up to manage the staffing side more effectively. As anybody who’s travelled or spent any time in an emergency room lately knows, a big part of this new phase of the pandemic has been the impact it’s had on the services that we rely on…that has had huge impacts on all aspects of our lives.”

‘High, high promise’

One of the strengths of the surface environmental testing approach is they sample surroundings, not individuals. Kassen said this gives researchers flexibility and doesn’t target specific people or require anyone to actively participate.

While it has some base costs, the method is also simple and cost-effective.

The surface environmental testing approach is still largely a research topic, but Kassen’s team is collaborating with physicians, public health officials and others to determine the most effective way to use it. He said Canada is at the forefront of the technology, and he believes it will prove a “really important tool.” 

Although there have been a few reports in academic journals that mention floor sampling for viruses, Kassen said he doesn’t quite understand why it hasn’t had the same traction as wastewater surveillance. 

“What we offer is a little more refined view of what’s going on at a smaller spatial scale,” he said. 

“I’m not aware yet of other jurisdictions using this regularly. I think that we might be the first. That’s exciting for us. We’d like to see it used, we think it has high, high promise, and we’re really excited.”

Kassen also sees the method as hugely beneficial to rural communities.

“Basically the burden in the wastewater is a signal of what’s going on in the community, and that’s awesome stuff. Wastewater doesn’t work so well if you’re in a rural community where you’re on a septic system,” he said. 

“So this was an opportunity for us to really work in collaboration with rural communities to help them keep track of what the burden of infection might be where wastewater won’t reach.”

He and his team will be working with other organizations and collaborators throughout the fall and winter to further refine their method. 

Happy to hear from potential Maritime collaborators

Beyond viruses, Kassen said the approach could be useful for tracking microbial resistance in bacteria and for fungi. He believes that his team and other researchers working on related topics have given Canada “a real opportunity to lead the world.” 

Over the next six months to two years, he hopes to see Canada become a world leader in environmental surveillance for microbial pathogens. 

“We’re continuing to work on it furiously and with enthusiasm,” he said.

If anyone in the Maritimes is interested in working with his team on a research project, Kassen said they’d like to hear from them and would happily entertain the possibility. 

“We’re hopeful that we can get this off and running and scale up the surveillance in a way that’s going to be most useful for Nova Scotians, Maritimers in general, Ontarians, Quebecers, the whole country, and even the world,” he said.