More than 10 per cent of COVID-19 tests are coming back positive in some pockets of Toronto

Thestar.com
October 6, 2020

More than 10 per cent of COVID-19 tests are coming back positive in some pockets of Toronto, a metric that shows the city’s second wave surging even more alarmingly than previously known and lends urgency to calls for local restrictions.

According to provincial data provided to the Star that has not been publicly released, approximately two-thirds of the city has a test-positivity rate of higher than 3 per cent, considered a critical threshold by public health authorities in Toronto and beyond.

Test positivity is an important statistic because it helps indicate how widespread transmission is, especially as testing or lab capacity fails to match demand -- as Ontario is experiencing right now. When people who need to be tested are turned off by long lineups or can’t find an available appointment at assessment centres, daily case counts may flatten or drop. But rising test positivity suggests surging transmission levels, independent of how many tests are completed.

Like all statistics, test positivity has its limitations. It can be temporarily boosted in an area by targeted testing or a major outbreak. Changes in testing criteria, such as Ontario’s move to swab many fewer people without symptoms, can also influence the rate.

But while low rates are difficult to interpret, high numbers “almost certainly” represent a worrying level of positive cases in the community, says Dr. Andrew Morris, an infectious disease specialist with Sinai Health and the University Health Network.

“Anything over 3 per cent is pretty high,” he said. “When you get over 8, 9 or 10 per cent, it’s very,very high.”

Three of the four areas of Toronto with test positivity rates over 10 per cent are in the city’s northwest corner: Weston and Finch, Sheppard and Jane, and Lawrence and Keele. This part of the city was also disproportionately hit by the first wave of the pandemic. Neighbourhoods in Toronto’s northwest corner have some of the highest proportions of low-income and racialized residents.

“The fact that resources and supports weren’t actively mobilized to make sure this couldn’t happen again in the same place speaks to the longstanding discrimination and structural racism,” said Dr. Andrew Boozary, a family physician in Toronto and executive director of Population Health and Social Medicine at University Health Network.

The fourth is the area just northeast of Yonge and Eglinton. Other areas with high test-positivity rates are spread across the city. Parts of Scarborough show rates above 7 per cent -- areas around Morningside Heights, Kennedy and Eglinton, and Ellesmere and Bellamy -- as do downtown zones like Trinity-Bellwoods, Church-Wellesley and St. James Town-Cabbagetown.

The previously unreported statistics buttress Toronto’s case that the city has reached crisis levels of virus transmission, requiring closures and restrictions to stop the spread. City officials maintain that the province alone has the legal authority to impose such measures, which include banning indoor dining and closing gyms for a month.

The province has countered that Toronto’s medical officer of health already has the legal authority to impose such measures. With the two levels of government at odds, restaurants and gyms continue to operate in the city -- even though other jurisdictions with similarly surging second waves have implemented harsher restrictions at much earlier stages of their second waves.

On Sunday, New York City moved to shut all non-essential businesses and close schools in nine hot spots where more than 3 per cent of recent tests came back positive for at least seven consecutive days.

Toronto Public Health also set a goal for the previous week’s citywide test positivity to remain under 3 per cent, according to its online dashboard of important indicators. The dashboard currently shows the rate at 2.5 per cent, but was last updated with data from the week of Sept. 20. The more recent data provided to the Star shows the citywide rate above 4 per cent.

Morris points to Melbourne, Australia, as a jurisdiction that took aggressive action as cases began to skyrocket a second time. The city has a population of 4.9 million, compared to Toronto’s 2.9 million.

In early July, officials in Melbourne announced a new lockdown when the city hit 97 active cases. Toronto had 97 new cases on Sept. 9, nearly a month ago.

In Melbourne, restaurants and bars were shuttered, classrooms went online, and residents were only allowed to leave home for work, school, caregiving, essential shopping and exercise. August brought yet more restrictions, with a nighttime curfew, widespread business shutdowns and a ban on travelling more than five kilometres beyond one’s home.

The lockdown was supposed to last six weeks. Three months later, the city’s second wave -- which far eclipsed its first -- is finally showing signs of coming under control.

Morris says Melbourne’s experience does not bode well for Toronto, which is in far worse shape than the Australian city was when it announced its second lockdown July 7. Ontario is grappling with a testing backlog of more than 65,000 samples, and Toronto Public Health has suspended contact tracing efforts for community cases, outside of outbreak settings.

“I have zero doubt that we are going to be experiencing something substantially worse than Melbourne has had to experience,” Morris said.

“It may not be deaths and ICU stays that do us in -- though it might be, that I just don’t know. But what I do know is the city will be brought to its knees just because of the overwhelming burden of cases and how that will make it unmanageable.”

Timing is critical when it comes to lockdown measures, and hesitating for even a single week could have enormous ramifications, according to studies from the pandemic’s first wave.

In May, a modelling study published in the journal Nature analyzed the timing and effectiveness of various interventions in China, including travel restrictions, lockdown measures, and the prioritization of early case identification and contact tracing.

The authors estimated that as of Feb. 29, China had 114,325 cases -- but that number could have been cut by 66 per cent if interventions had been triggered just one week earlier. And if China had hesitated an extra week before acting? Cases could have tripled, the researchers found -- and a three-week wait could have seen cases increase 18-fold.

A lot more has been learned about COVID since this paper, including the importance of superspreading events in the spread of this virus, said co-author Nick Ruktanonchai, a lecturer of infectious disease epidemiology with the University of Southampton in the United Kingdom.

But this only increases the urgency of imposing restrictions earlier rather than later, he said. Weighing in on Toronto’s situation, Ruktanonchai said he thought De Villa's proposed restrictions made sense -- but time is of an essence.

“If they act tomorrow, they’ll be much better off than if they act even a few days from now,”he said. “The one thing I think that we’ve learned about this pandemic is it’s not actually that hard to control -- as long as you’re decisive.”