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

New figures show Canadian housing prices outpacing those in other developed countries. (Black Press Media file photo)
Canadian housing prices fastest rising in the world

Relative to 2000, housing prices have risen by a factor of more than 2.5

Victoria’s economy is expected to bounce back fairly easily, according to a new report from BMO Capital Markets released April 15. (Black Press Media file photo)
Victoria in good position to bounce back post-pandemic, says BMO

City’s smaller size, lower COVID-19 caseload and diverse industry base bode well

Three new flight exposures have been reported departing from or arriving at the Victoria International Airport between April 7 and 11. (File photo/THE CANADIAN PRESS)
Three flight exposures reported at Victoria International Airport

One flight on April 7 and two on April 11 had confirmed cases of COVID-19 onboard

A case of COVID-19 has been confirmed at David Cameron Elementary School. People may have been exposed on April 14 to 16. (Black Press Media file photo)
COVID-19 exposure confirmed at Colwood elementary school

Exposure at Esquimalt’s Ecole Victor-Brodeur also confirmed

According to Statistics Canada, the unemployment rate in Greater Victoria rose to 5.7 per cent in March 2021, an increase of 0.8 per cent compared to February 2021. But the local unemployment rate remains the among the lowest in Canada. (Black Press Media File)
Greater Victoria’s unemployment rate rises to 5.7 per cent

The increase marks a reversal from recent months, but local economy among the strongest in Canada

Vancouver resident Beryl Pye was witness to a “concerning,” spontaneous dance party that spread throughout social groups at Kitsilano Beach on April 16. (Screen grab/Beryl Pye)
VIDEO: Dance party erupts at Vancouver’s Kitsilano Beach to the dismay of onlookers

‘It was a complete disregard for current COVID-19 public health orders,’ says Vancouver resident Beryl Pye

Flow Academy is located at 1511 Sutherland Avenue in Kelowna. (Michael Rodriguez - Capital News)
National fitness group condemns unlicensed Kelowna gym’s anti-vaccine policy

The Fitness Industry Council of Canada says Flow Academy is shining a negative light on the industry

People are shown at a COVID-19 vaccination site in Montreal, Sunday, April 18, 2021, as the COVID-19 pandemic continues in Canada and around the world. THE CANADIAN PRESS/Graham Hughes
Nothing stopping provinces from offering AstraZeneca vaccine to all adults: Hajdu

Health Canada has licensed the AstraZeneca shot for use in people over the age of 18

Deputy Prime Minister and Minister of Finance Chrystia Freeland responds to a question during Question Period in the House of Commons Tuesday December 8, 2020 in Ottawa. The stage is set for arguably the most important federal budget in recent memory, as the Liberal government prepares to unveil its plan for Canada’s post-pandemic recovery even as a third wave of COVID-19 rages across the country. THE CANADIAN PRESS/Adrian Wyld
Election reticence expected to temper political battle over federal budget

Opposition parties have laid out their own demands in the weeks leading up to the budget

A syringe is loaded with COVID-19 vaccine at a vaccination clinic run by Vancouver Coastal Health, in Richmond, B.C., Saturday, April 10, 2021. THE CANADIAN PRESS/Jonathan Hayward
B.C. to open up COVID vaccine registration to all B.C. residents 18+ in April

Registration does not equate to being able to book an appointment

Pat Kauwell, a semi-retired construction manager, lives in his fifth-wheel trailer on Maxey Road because that’s what he can afford on his pension, but a Regional District of Nanaimo bylaw prohibits using RVs as permanent dwellings, leaving Kauwell and others like him with few affordable housing options. (Chris Bush/News Bulletin)
Rules against RV living hard on Island residents caught in housing crunch

Regional District of Nanaimo bylaw forcing pensioner to move RV he calls home off private farm land

(Black Press file photo).
UPDATED: Multiple stabbings at Vancouver Island bush party

Three youths hospitalized after an assault in Comox

Selina Robinson is shown in Coquitlam, B.C., on Friday November 17, 2017. British Columbia’s finance minister says her professional training as a family therapist helped her develop the New Democrat government’s first budget during the COVID-19 pandemic, which she will table Tuesday. THE CANADIAN PRESS/Darryl Dyck
B.C. finance minister to table historic pandemic-challenged deficit budget

Budget aims to take care of people during pandemic while preparing for post-COVID-19 recovery, Robinson said

Most Read