Prevalence of Omicron BQ.1 subvariant rising in Saskatoon, wastewater data suggests

A newer Omicron subvariant may be driving a significant portion of COVID-19 cases identified in Saskatoon, new wastewater data suggests.

John Giesy, a University of Saskatchewan toxicology professor, shared wastewater data gathered by his team with news media Wednesday.

The data shows there is a general spike of the novel coronavirus in the city, particularly in the K444T spike mutation. The mutation is carried by multiple variants, including the Omicron BQ.1 subvariant, which is spreading throughout other parts of Canada and dozens of countries around the world.

"Based on that one mutation and what we know from other areas, BQ.1 is a likely candidate of what's driving the most recent blip that we've seen coming up in testing," Giesy said.

No data is available about the severity of illness or how the BQ.1 subvariant escapes immunity, according to a statement released on Oct. 27 by the World Health Organization's technical advisory group on SARS-CoV-2 Virus Evolution (TAG-VE).

However, the subvariant is growing at a much faster rate than other Omicron sublineages, including in Europe and the United States, the TAG-VE said.

BQ.1 is present in Saskatchewan and, according to the health ministry's latest Community Respiratory Illness Surveillance Program (CRISP) report, it is spreading.

The subvariant comprised 9.4 per cent of the COVID-19 specimens that were sequenced in a lab during the week of Oct. 9, the report says.

BQ.1.1, another Omicron subvariant, accounted for 15.6 per cent of sequenced specimens that week, the report adds.

Now, Giesy and his team are working to quantify how many people in Saskatoon are contracting COVID-19 through the BQ.1 subvariant. The trends they're seeing, he says, are similar to what's occurring in Ontario.

Each week, from Sept. 18 to Oct. 15, the BQ.1 subvariant accounted for a greater proportion of new COVID-19 cases in Ontario, according to Public Health Ontario's latest genomic sequence surveillance.

The subvariant accounted for about 0.5 per cent of cases identified in Ontario from Sept. 18 to 24, the report shows. But by the week of Oct. 9-15, it made up 3.1 per cent of identified cases.

By Nov. 2, the BQ.1 subvariant was projected to make up over 12 per cent of cases in Ontario, the report says.

Although the Saskatoon research team does not yet know exactly how many people might be affected by BQ.1, the wastewater data is an accurate way to decipher the prevalence of variants spreading in the city, said Ryan Ziels, an assistant professor at the University of British Columbia's school of civil engineering.

"Wastewater can give us an early warning, particularly when clinical testing is not as prescribed as it was earlier in the pandemic," said Ziels, who has conducted COVID-19 wastewater testing in the Vancouver Metro area.

"This could be useful information for public health to utilize in how they want to control the pandemic."

There is little known about BQ.1. It appears it can evade the antibodies produced by vaccines — as is often the case with Omicron and its subvariants — but vaccines should still protect people from severe illness should they contract the virus, according to TAG-VE.

At the same time, the Saskatchewan health ministry is monitoring all available information on BQ.1, as well as other variants of concern, and will use the data to inform the public health response, a spokesperson told CBC News in an email. 

The ministry advises residents to take precautions that could stymie the spread of COVID-19, including getting immunized, staying home when sick and wearing a mask, particularly when in crowded spaces indoors or areas with poor ventilation.