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

Just Posted

Students at Creston Valley Secondary School put together an art installation of a replica residential school room. (Photo by Kelsey Yates)
Creston students create art installation of residential school room

The replica was decorated with a small bed, school uniform, and notes written with pleas for help

A tent housing a mobile vaccination clinic. (Interior Health/Contributed)
Second dose vaccinations accelerating throughout region: Interior Health

To date, more than 675,000 doses have been administered throughout the region

The Food Recovery Program has pivoted to more meal production during this pandemic year. Submitted file
Kimberley Food Recovery Program producing more meals during pandemic

This past Monday, June 14, Shannon Grey-Duncan from the Kimberley Food Recovery… Continue reading

Prince Charles Secondary School
School District 8 votes in favour of name change for Secondary School in Creston

In an act of reconciliation, a new name will be chosen for Prince Charles Secondary School

Kootenay-Columbia MP Rob Morrison. Photo courtesy Conservative Party of Canada.
MP Morrison appointed to parliamentary national security committee

Kootenay-Columbia parliamentarian one of five candidates appointed to national security committee

Local environmental group Mainstreams conducting more work along the banks of Mark Creek. Paul Rodgers photos.
WATCH: Mainstreams continues riparian and aesthetic enhancement project along Mark Creek

Local environmental organization Mainstreams was back along the banks of Mark Creek… Continue reading

FILE – A science class at L.A. Matheson Secondary in Surrey, B.C. on March 12, 2021. (Lauren Collins/Surrey Now Leader)
Teachers’ union wants more COVID transmission data as B.C. prepares for back-to-school

BCTF says that details will be important as province works on plan for September

Provincial health officer Dr. Bonnie Henry outlines B.C.’s COVID-19 restart plan, May 25, 2021, including larger gatherings and a possible easing of mandatory masks on July 1. (B.C. government photo)
B.C. records 120 new COVID-19 cases, second vaccines accelerating

Lower Pfizer deliveries for early July, Moderna shipments up

A Heffley Creek peacock caught not one - but two - lifts on a logging truck this month. (Photo submitted)
Heffley Creek-area peacock hops logging trucks in search of love

Peacock hitched two lifts in the past month

Join Black Press Media and Do Some Good
Join Black Press Media and Do Some Good

Pay it Forward program supports local businesses in their community giving

The Calgary skyline is seen on Friday, Sept. 15, 2017. THE CANADIAN PRESS/Jeff McIntosh
2 deaths from COVID-19 Delta variant in Alberta, 1 patient was fully immunized

Kerry Williamson with Alberta Health Services says the patients likely acquired the virus in the hospital

The first suspension bridge is the tallest in Canada, with a second suspension bridge just below it. The two are connected by a trail that’s just over 1 km. (Claire Palmer photo)
PHOTOS: The highest suspension bridges in Canada just opened in B.C.

The Skybridge in Golden allows visitors to take in views standing at 130 and 80 metres

BC Green Party leader and Cowichan Valley MLA Sonia Furstenau introduced a petition to the provincial legislature on Thursday calling for the end of old-growth logging in the province. (File photo)
BC Green leader Furstenau introduces old-growth logging petition

Party calls for the end of old-growth logging as protests in Fairy Creek continue

B.C. Premier John Horgan leaves his office for a news conference in the legislature rose garden, June 3, 2020. (B.C. government photo)
B.C. premier roasted for office budget, taxing COVID-19 benefits

Youth addiction law that triggered election hasn’t appeared

Most Read