Toronto Public Health begins sharing more coronavirus testing data for neighbourhoods

Toronto Public Health (TPH) has begun to share more coronavirus data in regards to specific neighbourhoods, including the per cent positivity rate, but it’s warning the data in isolation won’t tell the full story of what is going on.

Following a leak of incomplete data showing the per cent positivity rate of testing in a Toronto neighbourhood, TPH officials said they would begin sharing the data when they could.

Per cent positivity measures the proportion of people testing positive out of the total number who were tested. It alone, officials noted, won’t give an accurate portrayal of what is happening in an area, which is why the data is being provided with details of testing numbers as well.

TPH has already been providing neighbourhood case data for months.

Testing is under the purview of the Ontario government, but that data is shared with the City of Toronto. At Monday morning’s Board of Health meeting, TPH officials explained why the per cent positivity data should be considered with other factors.

Sarah Collier, TPH’s manager of surveillance and epidemiology, said per cent positivity is most meaningful when combined with other indicators, like case counts and testing rates. When all of those figures are high, it is indicating a high degree of virus circulation.

Currently, Toronto’s overall per cent positivity rate is 3.1 per cent.

Collier used an example of how the data can help direct the response from a neighbourhood level by looking at Rustic in the city’s northwest, bordered by Jane Street, Culford Road and Lawrence Avenue West and Highway 401.

For the week of Sept. 27, the neighbourhood had a per cent positivity rate of 14.3 per cent. But the case rates between Sept. 25 and Oct. 15 were 191 per 100,000 people and the testing rate was 9.9 per 1,000 people.

Collier suggested when looked at together, the high per cent positivity may be driven by testing capacity or a low number of people being tested. Data showed it was one of the lowest numbers for testing per neighbourhood for that week.

“For many neighbourhoods in the northwest, we are seeing a high per cent positivity and low testing rates and case rates in the high-to-mid range and there is some variation over time, but in general this means that there should be more testing in these areas to understand what is happening in these areas,” said Collier.

In contrast, Collier presented findings from Little Portugal closer to Toronto’s centre, where per cent positive rates were over seven per cent and the testing rate was the second-highest in the city.

The data, she said, should be used to indicate where there is a need for more testing or where there is a need for more COVID-19 measures.

“Alone, per cent positivity can lead to incorrect conclusions, stigmatizing conclusions,” said Collier.

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But presented with other data, she said it can help you understand what is going on.

The move to provide more data is a step toward more transparency, but the per cent positivity will not always be made public. In some cases, TPH will intentionally suppress the information if there are privacy concerns.

Throughout the pandemic, there has been heightened interest in how the virus has disproportionately affects racialized people. In April, TPH began gathering socio-economic information from those who tested positive.

But on Monday, Dr. Eileen de Villa, Toronto’s medical officer of health, revealed that gathering that information was paused at the beginning of October due to the surge in cases. The pause began on Oct. 2 and ended on Oct. 9, she said.

The board voted in favour of several recommendations to address the issue, including the development of an equity action plan on COVID-19 with all levels of government, requesting the Ontario government make testing more available in areas of high transmission along with asking for a provincial stay on all residential evictions.