Finding Clues To The Covid Outbreak In Our Sewage

Sewage can act as an early warning system for COVID-19 spikes in a community or institution, Ottawa researchers have found.


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And a more sensitive method of testing that sewage, developed by a team led by Dr. Alex MacKenzie, senior scientist at the CHEO Research Institute, could make the early warning system more effective.

Ottawa researchers say they would eventually like to see wastewater surveillance expanded to pilot projects across the province that could test communities as well as schools and long-term care homes in real time.

Since the pandemic began, a team of Ottawa researchers has been looking in the sewers for answers about the spread of COVID-19. What they have found and developed could be game-changers in helping to control spread of the disease.

The data produced by analyzing wastewater can predict COVID-19 outbreaks days before people begin showing symptoms and getting tested — something that could potentially help to reduce outbreaks in institutions and schools.

uOttawa engineering professor Robert Delatolla, MacKenzie, and a team of researchers have produced one paper — not yet peer reviewed or published — showing that their analysis of wastewater in Ottawa and Gatineau is useful in tracking the number of COVID-19 cases in a community.

“In the absence of an effective vaccine to prevent COVID-19 it is important to be able to track community infections to inform public health interventions aimed at reducing the spread and therefore reduce pressures on health-care units, improve health outcomes and reduce economic uncertainty,” the authors wrote, adding that wastewater surveillance has emerged as an effective tool to do so.

This summer, after that research paper had been submitted, they found out just how useful data gathered from wastewater could be.

In mid-July, the daily COVID-19 case count suddenly spiked from single digits to new daily cases in the upper 20s in Ottawa. When researchers looked at the data around that time, they found the spike showed up in wastewater two days before it started showing up in tests.

“We caught it two days before the daily numbers went up and four days before an associated increase in the hospitalizations,” said Delatolla.

That is significant and suggests, if available in real time, wastewater surveillance could give public health officials more information to act sooner.

Research being led by the CHEO Research Institute’s MacKenzie, could make that surveillance tool more accurate and potentially give public health officials an even earlier warning system by tracking proteins instead of RNA.

Wastewater surveillance has, so far, been done by measuring RNA in SARS-CoV-2, the virus that causes COVID-19. But that can be tricky, especially when case counts are low. RNA tends to be fragile and breaks down in the wastewater, said MacKenzie.

He has developed a means of tracking SARS-CoV-2 by looking at proteins associated with the virus. He believes he is the first in the world to do so. The advantage, MacKenzie said, is that protein signals the presence of SARS-CoV-2 at a rate thousands of times higher than RNA does, which means the warning signal of an outbreak would be stronger and earlier and case levels could be more accurately measured even when they are low.

Wastewater surveillance is now being used around the world to track COVID-19 cases and is being studied across Canada.

Officials at the University of Arizona said last week they may have been able to prevent a large outbreak on campus after getting a positive sample in sewage from one of the university’s dorms. After testing more than 300 people who live or work there, they found two asymptomatic students who were positive and isolated them. Wastewater testing is also being used in other parts of the world.

Delatolla said the sewage system is built so that wastewater can be collected at individual sites, as officials at the University of Arizona did. It offers the possibility of narrowing the source of a spike early and taking action.

“Maybe now we can monitor the long-term care homes and make sure that we catch it early.”

The scientists, who say they have had to scrape together funding to keep the research going, are scrambling to get their research published. They have sent details of their work to the province’s scientific table on COVID-19, which looks at the scientific and research response to the pandemic. They are hoping for funding to use the knowledge to help lessen the impact of the pandemic.

In a written statement, Ottawa Public Health called the work promising but still in early days when it comes to “ reliably seeing an increasing signal from sewage before it is seen from human test surveillance.

“Ottawa Public Health is in regular contact with the uOttawa researchers and is hopeful that one or more facets of this work will contribute to COVID-19 surveillance activity in the near future.”

Meanwhile, MacKenzie, who usually does research on rare diseases in children, said the pandemic has opened a new world for him — underground — trying to work with researchers like Delatolla to make a difference.

“It is like life during war time: It is stressful and a tragedy but at the same time the better part of humanity comes out.”

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