Raw sewage being flushed into Alberta’s municipal wastewater plants could help public health officials better track — and predict — the spread of COVID-19.
A team of Alberta scientists has joined a growing international effort to sample wastewater for traces of SARS-CoV-2, the virus responsible for the disease.
Labs at the University of Alberta and the University of Calgary are among more than a dozen across Canada either actively testing or working to help establish a standard methodology for sampling.
Researchers behind the ongoing national pilot project hope the sample testing will serve as an early warning system for community infections — helping to identify new or intensifying outbreaks.
Clinical testing don’t let you sample everybody, but sewage does sample everybody.”-Steve Hrudey
“How quickly can results be produced and will it be possible to deliver that advance warning? That’s one of the questions we’re trying to nail down,” said Steve Hrudey, a professor emeritus in the Department of Laboratory Medicine & Pathology at the University of Alberta.
“And that isn’t the only value of getting this. The reality is, the logistics of clinical testing don’t let you sample everybody, but sewage does sample everybody.”
In his role as chair of the National Research Advisory Group under the Canadian Water Network, Hrudey is helping to spearhead the research.
The project is called the COVID-19 Wastewater Coalition — and it’s helping co-ordinate the work of researchers across the country, providing technical guidance to scientists, laboratories, wastewater utilities and public health authorities.
Researchers are relying on the expertise of scientists in the United States and Europe, where COVID-19 testing of sewage has already been more widely adopted, Hrudey said.
“We’re basically following early studies that were done in the Netherlands, where they collected from sewage treatment plants at a number of sites and used genetic marker methods to try and detect the signal from SARS-CoV-2.
“Once that information was public, there was an explosion of interest around the world.”
‘Not a magic bullet’
The testing examines raw excrement for tiny genetic RNA fragments of the virus. By concentrating the samples, small sequences of single SARS-CoV-2 genes can be detected. The analytical technique is called polymerase chain reaction (PCR).
The testing cannot identify how many people in a given community are infected. Only some people who are sick actually excrete the virus in their stools but the traces of the virus can appear before symptoms develop.
Researchers say sewage surveillance could prove useful in large municipalities and on a smaller scale, tracking isolated or vulnerable communities through regular testing of plumbing systems in prisons, schools, homeless shelters, hospitals or care homes.
There is currently no standard test for the analysis. By refining their methodology for sampling, researchers hope to give health officials a way to better track viral spread and target testing within communities.
“We definitely want to make sure that the data that’s generated is, you know, worth the paper it’s ultimately going to get written on,” Hrudey said.
“We’ve recognized that this is not a magic bullet. There’s never going to be any prospect that this somehow replaces clinical testing. The idea is to supplement our understanding of what’s going on with an epidemic.”
Alberta sampling remains experimental
The study in Alberta, funded by the Canadian Institutes of Health Research, is being led by Dr. Lilly Xiaoli Pang, a University of Alberta professor and molecular virologist at Alberta Precision Laboratories – Public Health Lab.
Samples are taken two to three times a week from water plants and sent for testing in Calgary. The results, supplied to Alberta Health Services, are not being released to the public while research is underway.
“The persistence of the virus genetic material in the stool samples is yet to be studied,” Alberta Health Services spokesperson Kerry Williamson said in a statement.
“Further work is required to understand the meaning of positive and negative results and the changes of the level of virus in wastewater in Alberta. Locally and nationally there are ongoing discussions on how to analyze and display this type of data so that it is a helpful tool for public health management.”
We’ve been trying to warn people from the beginning, it’s complicated.– Steve Hrudey
Though most of the testing in Canada remains experimental, Ottawa Public Health recently began using the data daily, and recent sampling shows the concentration of COVID-19 in the city’s wastewater has doubled in the past month, and is now 10 times higher than it was in June.
In the United States, health officials say sampling helped avoid a potential outbreak at the University of Arizona. When tests of wastewater at the dorms came back positive for COVID-19, two asymptotic students were identified and quickly quarantined.
Wastewater surveillance is not new. Human excrement has offered valuable health information on the presence of viruses, disease and drug use for decades.
When it comes to tracking for COVID-19, however, translating the data gathered into useful public health information will take time, Hrudey said.
Phase one of the research, which is nearly complete, has been complicated by supply chain issues around lab equipment and supplies, and often, a lack of funding.
If sewage testing is to be relied upon as a surveillance method, the testing itself will need to be done quickly and efficiently so public health officials are provided reliable advance warnings, Hrudey said.
A co-ordinated response is needed in Canada, especially as case numbers continue to increase.
“Even if everything runs 100-per-cent smoothly, there is a lag time,” he said. “We’ve been trying to warn people from the beginning, it’s complicated.”