Data ‘lagging’ to measure spread, experts say

As lockdown eases, concerns raised over tracking cases of virus outside institutions

Ontario needs much more up-to-date data about the spread of COVID-19 in the community before the provincial economy can be fully reopened, epidemiologists warn.

As Ontario’s economy begins to lurch back to life this week with curbside pickup available Monday at retail stores with street entrances, crucial data on the prevalence of the virus in the community is still lacking.

While in theory we should be able to

“I know that there’s an urgency to open the economy for various reasons, but if you’re basing it off of data that you’re seeing today, it’s not the full picture.”

Todd Coleman, epidemiologist and assistant professor in health sciences at Wilfrid Laurier University

figure out how many people have the virus in the community — those cases not in long-term-care facilities, retirement homes or hospitals — this has proved impossible with any degree of accuracy. The Star showed last week that delays, inconsistencies in the way cases are reported and data gaps mean no one can say for sure how far the virus may be spreading outside of the province’s institutional settings.

“It’s like trying to point a flashlight at a moving mouse in a dark room. With lagging data, you’re always pointing the light to where the mouse was, not where it currently is,” said Raywat Deonandan, an associate professor and epidemiologist with the University of Ottawa. He noted that data delays are largely unavoidable but add a layer of difficulty to decision-making.

“The challenge is in making resource decisions today about a situation that is likely days old.”

Currently, Public Health Ontario publicly reports COVID-19 cases and deaths through its integrated Public Health Information System (iPHIS), which relies on local public health units to manually enter detailed case information.

The Star has found this reporting system has been prone to under-reporting the up-todate number of cases. The publicly reported version of the data also does not say where there are clusters in the community.

The Ministry of Long-Term Care separately publishes its own data on cases and deaths in long-term-care facilities. Because these numbers do not require the manual entry of detailed case information, the ministry’s numbers have been more up to date than those coming out of iPHIS, meaning comparison between the two sets of information is not possible.

Dr. David Williams, the province’s chief medical officer of health, said Monday that of 308 new COVID-19 cases reported in Ontario in the previous 24 hours, somewhere between 140 and 160 are in the community. He said officials are working to cut down the amount of time it takes to get confirmation on the true number of community cases — a process that he said last week could take as many as seven days.

Delays could result from people getting tested for the virus at assessment centres outside their home health units or lab slips filled out with incomplete information, Williams said, meaning that cases may not be getting entered into iPHIS quickly.

He said local public health units are aiming to ramp up contact tracing so that 90 per cent of the people who came into contact with someone who tested positive for the virus are notified within 24 hours after the test result. This should speed up local public health units’ entering of cases into the database, he said.

Williams added that Public Health Ontario is moving toward indicating on its website which cases resulted from community spread.

As of 5 p.m. Monday, the Star tallied 21,947 confirmed or probable cases of COVID-19, including 1,773 deaths, using data from local public health units. These data are more up-to-date than what the province publishes through iPHIS, which reported 20,546 confirmed cases Monday and 1,660 deaths.

“I know that there’s an urgency to open the economy for various reasons, but if you’re basing it off of data that you’re seeing today, it’s not the full picture,” said Todd Coleman, epidemiologist and assistant professor in health sciences at Wilfrid Laurier University.

“If we still have any extent of community level spread and you start reopening things, that’s not ideal in terms of trying to reduce the potential for transmissions,” he said.

Under ideal circumstances, “you would want the most upto-date information to get an accurate reflection of what current spread looks like,” Coleman said.

The incomplete data may give a false sense of security that leads people to stray from physical distancing guidelines, Deonandan said. People may “falsely assume that because the majority of growth is in residences … the open communities are totally safe.”

“We must be diligent in our public health discipline to prevent a resurgence of cases,” he said.

“If we still have any extent of community level spread and you start reopening things, that’s not ideal in terms of trying to reduce the potential for transmissions,”

TODD COLEMAN EPIDEMIOLOGIST