Wastewater monitoring suggests COVID-19 transmission may have peaked in Winnipeg on New Year's Day

Despite record numbers of COVID-19 patients in hospital and multiple daily deaths, there is some evidence the pandemic's current wave could be receding in Manitoba.

Wastewater monitoring conducted by the National Microbiology Laboratory suggests the virus that causes COVID-19 was found in the largest quantities in Winnipeg at the beginning of January.

Samples collected at each of Winnipeg's three sewage-treatment plants suggest the viral load in Manitoba's capital peaked on New Year's Day, Manitoba Public Health said in a statement.

The province is now working with scientists at the National Microbiology Lab to analyze the data, said public health.

The province has yet to conclude the pandemic's current wave of cases is drawing down.

"Wastewater surveillance is one tool and can be a helpful indicator, but there can be considerable fluctuation in the data, which means it needs to be considered in concert with other data," Manitoba Public Health's statement said.

"While this information shouldn't be used in isolation, previous studies have shown that wastewater data can be an early indicator to identify new strains, and increasing or decreasing volumes."

The National Microbiology Laboratory, located on Arlington Street, has been analyzing samples of Winnipeg wastewater since the start of the pandemic.

People who are infected SARS-CoV-2, the coronavirus that causes COVID-19, shed viral RNA in their feces. This shedding can start before infected people even develop symptoms, and can continue for several weeks.

The RNA can be monitored in wastewater and used to detect COVID-19 outbreaks, determine whether infections are rising or dropping and even discern trends, such as the effects of new restrictions or pandemic policy decisions like sending kids back to school.

WATCH | A March 2021 report on how wastewater monitoring helps detect COVID-19: 

How does wastewater help with surveillance of COVID-19?

4 years ago

Duration 4:19

Ottawa has been testing its wastewater to get a better understanding of how much of the coronavirus is in the city's sewage. The project's co-lead investigator explains how it helps with surveilling COVID-19.

"Wastewater surveillance signals do follow trends in cases quite closely," said Anna Maddison, a spokesperson for the Public Health Agency of Canada.

"Therefore, wastewater data allows us to identify large outbreaks, such as the recent Omicron wave, and declines in community transmission due, for example, to public health measures."

Monitoring data not made public in Manitoba

Dr. Philippe Lagacé-Wiens, a medical microbiologist at St. Boniface Hospital, said wastewater monitoring became a more important tool after the highly contagious Omicron coronavirus variant became dominant, and transmission became so widespread that most provinces lost the ability to monitor it.

"It certainly is more important now that PCR testing is not as reliable as it was," he said.

Health authorities in Saskatchewan, B.C., some regions of Ontario and elsewhere make wastewater monitoring data public. Manitoba does not, even though the National Microbiology Laboratory sends results twice a week for the province to analyze.

"It really feels like a lack of transparency," Lagacé-Wiens said. "I'm not saying anybody has anything to hide, but when people are not transparent, the immediate conclusion is that there's something to hide."

Lagacé-Wiens said he can't conclude much from being told the COVID-19 viral load peaked on Jan. 1.

"It's easy to say that there was a peak around Jan. 1, but without actually knowing what's been going on since … it's hard to say if it's really on the downswing or if there's been significant changes since that peak."

It's also possible COVID-19 transmission is declining in Winnipeg and still rising elsewhere in the province, he added.

In regions where Omicron was first detected, such as South Africa, the U.K. and the U.S. eastern seaboard, COVID-19 hospitalizations and deaths have persisted in high numbers even after transmission rates dropped.

A record 729 Manitobans were in hospital with the illness on Tuesday, while the province has announced an average of five COVID-19 deaths per day this month.