Motorists wait to enter a Fraser Health COVID-19 testing facility, in Surrey, B.C., on Monday, November 9, 2020. THE CANADIAN PRESS/Darryl Dyck

Motorists wait to enter a Fraser Health COVID-19 testing facility, in Surrey, B.C., on Monday, November 9, 2020. THE CANADIAN PRESS/Darryl Dyck

COVID-19: What do rising positivity rates mean for B.C.? It’s not entirely clear

Coronavirus cases are on the rise but the province has not unveiled clear thresholds for further measures

If you’ve been watching the news, you’ve probably seen it: an exponential increase in COVID-19 cases, as well as a recent spike in deaths.

But a less-reported number is the positivity rate, which the B.C. Centre for Disease Control “has increased steadily and steeply” in recent weeks. In the week of Nov. 8-14, it rose to above six per cent according to a situation report released by the organization, hitting a level that is above anything seen during the first wave of COVID-19 this spring.

The maximum positivity rate during the first wave hit five per cent in April, but occurred when testing was much less widespread and targeted at high-risk individuals. The number of tests at the time was about nine times lower than it was during November, at only 7,500 tests compared to about 70,000 currently. For context, the positivity rate in the first half of October was under two per cent.

“That rate is the fraction of the number of positive tests that come back divided by the total number of tests,” said Daniel Coombs, a mathematics professor at the University of B.C. Positivity rates are typically more accurate when more people are being tested.

B.C.’s increasing positivity rate in recent weeks is doubly concerning because the number of weekly tests has stayed between 60,000 and 70,000 even as the positivity rate rose from 1.82 per cent to six per cent.

B.C.’s positivity rate has reached record highs in November 2020 as the province struggles with the second wave of the COVID-19 pandemic. (B.C. Centre for Disease Control)

“If you suddenly have more positive people and the number of tests stayed the same, then [the rate] would go up,” Coombs told Black Press Media by phone.

“You don’t want this number to test rapidly unless your testing policy is also changing rapidly, and that’s not the case, so having it go up is probably a bad sign. It’s indicating we are finding more.”

The positivity rate backs up what the daily case count and rising hospitalizations are saying: the number of people with COVID-19 in B.C. is on the rise, with health officials attributing much of the spread to private social gatherings and high-risk exercise classes. B.C hit a record 762 cases cases Wednesday (Nov. 18) and recorded its deadliest day of the pandemic on Tuesday with 11 deaths.

To put B.C.’s six per cent positivity rate into context, Coombs points to Stockholm in Sweden which has a positivity rate of about 20 per cent, or one in five people testing positive. Sweden, which has refused to bring in lockdowns, has an overall positivity rate of above 10 per cent.

Canada’s overall rate has about 6.6 per cent of tests coming back positive.

But what B.C.’s rising positivity rate means is hard to tell. B.C. imposed region-specific restrictions for the Lower Mainland on Nov. 7, which heavily limited gatherings of any size in public or private, and expanded those restrictions – and brought in a mask mandate – province-wide on Thursday (Nov. 19). However, the preliminary positivity rate reported on the B.C. CDC COVID dashboard for Thursday (Nov. 19), the last day public data was released prior to an expected drop this Monday afternoon, was even higher than it was prior at 6.7 per cent. The Fraser Health positivity rate reported Thursday is at 9.6 per cent, in line with the region having a disproportionally high number of new cases. But positivity rates are rising in other regions too, with Vancouver Coastal Health at 5.1 per cent and Northern Health at 5.3 per cent as of Thursday. Interior Health was at a 3.5 per cent positivity rate, while Island Health is at 1.4 per cent.

READ MORE: 6 things you need to know about B.C.’s latest COVID-19 health orders

READ MORE: Masks now mandatory in all public indoor and retail spaces in B.C.

B.C. has not publicly linked any particular positivity rate to levels of COVID-19 restrictions like other regions. In Ontario, positivity rates are tied into the COVID-19 response framework, the plan that sets out when certain restrictions will come into place. At above 2.5 per cent, Ontario would enter the most restrictive level of COVID-19 measures short of a full lockdown. In New York City, schools shut down last week because the city’s positivity rate reached its three per cent threshold. In May, the World Health Organization recommended that the rate remain below five per cent for at least two weeks before governments consider reopening.

Provincial health officer Dr. Bonnie Henry said that rate is being monitored, but not what higher rates could lead to.

“Per cent positive is something we watch,” said Henry. “It’s one of those metrics that if it’s above five per cent… that tells us there’s transmission in the community that is concerning. We’d like to see it lower.”

READ MORE: B.C. education minister wants to avoid school closures completely

READ MORE: B.C. records 516 more COVID-19 cases, 10 new deaths

READ MORE: More COVID-19 testing needed for senior home staff, B.C.’s advocate says


@katslepian

katya.slepian@bpdigital.ca

Like us on Facebook and follow us on Twitter.

Want to support local journalism during the pandemic? Make a donation here.

Coronavirus

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

The Art Infiniti Hotel caught fire on New Year’s Eve (Dec. 31, 2020) in Maple Ridge. Seven people were evacuated safely. (Barry Brinkman/Special to The News)
LETTER: Headline about Maple Ridge fire victim insensitive

Senior lost everything in Dec. 31 fire and letter writer felt denture reference inappropriate

Maple Ridge released its winter program guide recently. (Special to The News)
City unveils numerous winter programs and activities

Maple Ridge unveils guide that takes into consideration COVID-19

Corina Ardelean, right, and a volunteer wait for clients at Christian Life Assembly in Maple Ridge. (Special to The News)
Romanian refugees fulfill mission in Maple Ridge

Helping struggling families put food on the table

Maple Ridge’s Bruce Coughlan. (Special to The News)
Robbie Burns day to be feted virtually by Maple Ridge musician

Bruce Coughlan will hold virtual concert in Campbell River theatre in honour of Scottish bard

Naturally Splendid employees working at a flow wrapper station at its facility in Pitt Meadows (Special to The News)
Plant-based Pitt Meadows business pivots during pandemic

Naturally Splendid partners with Australian company on bringing meat substitute to Canada

A scene from “Canada and the Gulf War: In their own words,” a video by The Memory Project, a program of Historica Canada, is shown in this undated illustration. THE CANADIAN PRESS/HO - Historica Canada
New video marks Canada’s contributions to first Gulf War on 30th anniversary

Veterans Affairs Canada says around 4,500 Canadian military personnel served during the war

Williams Lake physician Dr. Ivan Scrooby and medical graduate student Vionarica Gusti hold up the COSMIC Bubble Helmet. Both are part of the non-profit organization COSMIC Medical which has come together to develop devices for treating patients with COVID-19. (Monica Lamb-Yorski photo - Williams Lake Tribune)
Group of B.C. doctors, engineers developing ‘bubble helmet’ for COVID-19 patients

The helmet could support several patients at once, says the group

A 17-year-old snowmobiler used his backcountry survival sense in preparation to spend the night on the mountain near 100 Mile House Saturday, Jan. 16, 2021 after getting lost. (South Cariboo Search and Rescue Facebook photo)
Teen praised for backcountry survival skills after getting lost in B.C.’s Cariboo mountains

“This young man did everything right after things went wrong.”

Conservative Leader Erin O’Toole holds a press conference on Parliament Hill, in Ottawa on December 10, 2020. THE CANADIAN PRESS/Sean Kilpatrick
No place for ‘far right’ in Conservative Party, Erin O’Toole says

O’Toole condemned the Capitol attack as ‘horrifying’ and sought to distance himself and the Tories from Trumpism

Cannabis bought in British Columbia (Ashley Wadhwani/Black Press Media)
Is it time to start thinking about greener ways to package cannabis?

Packaging suppliers are still figuring eco-friendly and affordable packaging options that fit the mandates of Cannabis Regulations

A passer by walks in High Park, in Toronto, Thursday, Jan. 14, 2021. This workweek will kick off with what’s fabled to be the most depressing day of the year, during one of the darkest eras in recent history. THE CANADIAN PRESS/Chris Young
‘Blue Monday’ getting you down? Exercise may be the cure, say experts

Many jurisdictions are tightening restrictions to curb soaring COVID-19 case counts

Pindie Dhaliwal, one of the organizers for the Surrey Challo protest for Indian farmers. She says organizers were told by Surrey RCMP that the event was not allowed due to COVID-19. Organizers ended up moving the protest to Strawberry Hill at the last minute. (Photo: Lauren Collins)
Indian farmers rally moves as organizers say Surrey RCMP told them they couldn’t gather

Protest originally planned in Cloverdale, moved to Strawberry Hill

A health-care worker prepares a dose of the Pfizer-BioNTech COVID-19 vaccine at a UHN COVID-19 vaccine clinic in Toronto on Thursday, January 7, 2021. THE CANADIAN PRESS/Nathan Denette
COVID-19: Provinces work on revised plans as Pfizer-BioNTech shipments to slow down

Anita Anand said she understands and shares Canadians’ concerns about the drug company’s decision

Tourists take photographs outside the British Columbia Legislature in Victoria, B.C., on Friday August 26, 2011. A coalition of British Columbia tourism industry groups is urging the provincial government to not pursue plans to ban domestic travel to fight the spread of COVID-19. THE CANADIAN PRESS/Darryl Dyck
B.C. travel ban will harm struggling tourism sector, says industry coalition

B.C. government would have to show evidence a travel ban is necessary

Most Read