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

Andre Robert won $500,000 through a Lotto Extra ticket on Dec. 23, 2020. Photo: Jeanne d’Arc Allard
Creston resident wins $500k through Lotto ticket

“I was surprised. I wasn’t sure if it was true or not.”

A stroll through the Wildlife Management Area. Photo: Margaret Miller
Valley Views: IT’S ABOUT TIME

“Time often feels elastic, but one thing is certain. It never stands still. Winters come and go, some more difficult than others. Months become years; years become decades. And in our busy human world, pandemics can happen. And linger over time. And pass.”

Summit Ski Hill had a delayed start to the season because of warm temperatures. Photo: Summit Ski Hill
Late season start frustrating for Nakusp ski hill

Summit Ski Hill only just opened Jan. 14

Four friends were heading to their home on Highway 6 just south of Silverton on the evening of Dec. 25, 2020, when the people in the front of the vehicle saw what looked like a “huge, man-like figure” on the side of the road. (Pixabay.com)
Possible Bigfoot sighting shocks, excites Silverton residents

‘I didn’t see the creature myself, I saw the prints’

A woman wearing a protective face mask to curb the spread of COVID-19 walks past a mural in Victoria, B.C., on Monday, Dec. 7, 2020. THE CANADIAN PRESS/Marissa Tiel
115 new COVID-19 cases, no new deaths in Interior Health

There are now a total of 4,970 cases in the region

A woman wears a face mask and shield to curb the spread of COVID-19 while walking in North Vancouver, B.C., on Wednesday, January 6, 2020. THE CANADIAN PRESS/Darryl Dyck
536 COVID cases, 7 deaths reported as B.C. finds its first case of South African variant

Henry said 69,746 people have received their first dose of the COVID vaccine.

Seasonal influenza vaccine is administered starting each fall in B.C. and around the world. (Langley Advance Times)
After 30,000 tests, influenza nowhere to be found in B.C.

COVID-19 precautions have eliminated seasonal infection

Martin Luther King Jr. addresses the crowd during the march on Washington, D.C., in August of 1963. Courtesy photo
Government announces creation of B.C.’s first anti-racism act on Black Shirt Day

B.C. Ministers say education “a powerful tool” in the fight for equity and equality

Jobs Minister Ravi Kahlon shared a handwritten note his son received on Jan. 13, 2021. (Ravi Kahlon/Twitter)
Proud dad moment: B.C. minister’s son, 10, receives handwritten note for act of kindness

North Delta MLA took to Twitter to share a letter his son received from a new kid at school

Purcell Wilderness Conservancy expanded with 18 hectares of previously privately-owned land. Photo from BC Parks.
Purcell Wilderness Conservancy expanded following Provincial land acquisition

18 hectares of waterfront added to critical wildlife habitat

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

Black Press media file
Port McNeill driver tells police he thought the pandemic meant no breathalyzers

Suspect facing criminal charges after breathalyzer readings in excess of 3.5 times the legal limit

Forestry companies in B.C. agree to abide by the cedar protocols based on traditional laws of the First Nation members of the Nanwakolas Council. (Photo courtesy, Nanwakolas Council)
Landmark deal sees B.C. forest firms treat big cedars like a First Nation would

Western Forest Products, Interfor among companies to adapt declaration drafted by Nanwakolas Council

A northern resident killer whale shows injuries sustained by a collision with a vessel in B.C. waters. (Photo supplied by Ocean Wise Conservation Association)
Coast Guard ramps up protections for B.C. whales

First-ever Marine Mammal Desk will enhance cetacean reporting and enforcement

Most Read