Wastewater COVID testing rising to the occasion

As some places limit PCR testing for COVID-19 and redeploy contact tracing staff to vaccination efforts, experts have stressed that daily case counts no longer paint the full picture of viral levels within communities.

Researchers at the Great Lakes Institute for Environmental Research (GLIER) believe wastewater testing continues to give the most accurate metric to determine where viral activity is propagating.

“It’s gone from what was essentially a pilot, to now being a tool that public health is relying on,” says Executive Director Dr. Mike McKay.

He says public health demand for wastewater testing across Ontario has grown since early 2020, noting University of Windsor researchers have been undertaking wastewater surveillance since early in the pandemic, looking for trace amounts of the virus in sewage to see how it's spreading.

McKay says health officials are really becoming more dependant on this metric, and GLIER staff are trying to rise to the occasion and provide that information.

The Windsor-Essex County Health Unit (WECHU) reported 353 new cases of COVID-19 on Wednesday along with two additional deaths.

“We have to make a big shift at this point in time about how we assess the burden of illness,” said Acting Medical Officer of Health, Dr. Shanker Nesathurai on Wednesday.

Nesathurai says several metrics like the number of people with COVID in hospital, the intensive care unit, on a ventilator, those who have died and the level of absenteeism at schools and places of work all need to be considered with wastewater results to get an idea of how severe the virus is locally.

“Use of wastewater testing is one inferential piece of data that we could use to evaluate the burden of illness,” said Nesathurai.

He notes local public health staff are waiting for the province to update the framework of how to measure COVID spread, so they can make informed decisions.

“Either way, if the province, when the province formulates its guidance, we will incorporate that and if we have to add local indices which serve a local purpose, we can do that as well moving forward,” Nesathurai explained.

Meantime, the team at GLIER is ramping up current efforts after the holiday season caused delay.

“We scaled back in terms of our frequency of testing over the holidays,” McKay tells CTV News. “The wastewater plants had reduced personnel over the holiday season. We’re actually catching up this week.” McKay explains. “We collected samples, some of them were processed, but we went from basically three times a week to one time a week over the last couple weeks. So, stay tuned, we should be caught up by the end of this week.”

McKay says early indications point to a rapid increase of COVID in local wastewater in Windsor-Essex and Chatham-Kent, anticipating levels to continue to rise given the dynamics of clinical test availability and the range of severity with Omicron symptoms.

“We are anticipating that Omicron is probably close to 100 per cent of the virus right now.”

McKay adds, “We’re hoping that this will be a relatively short resurgence of the virus, so, we’re going to redouble our efforts and increase frequency of sampling over the next few weeks, to really provide the most unbiased information to the public health units.”