Why limited contact tracing could slow Ontario's plan to end COVID-19 restrictions

It's not clear when Ontario will be able to hit one of its key targets for phasing out emergency measures: rapid contact tracing for every new confirmed case of COVID-19. 

The provincial government's framework for reopening Ontario's economy in stages sets out criteria for starting to ease the restrictions imposed to slow the spread of the novel coronavirus. The benchmark set for the public health system is that "approximately 90 per cent of new COVID-19 contacts are being reached by local public health officials within one day."

How close is Ontario to achieving that target? Asked on Monday, the province's chief medical officer did not provide a clear answer.

Instead, Dr. David Williams likened contact tracing to a police investigation: interviewing the person who tested positive, trying to get them to recall who they've been in contact with, following up by interviewing all those contacts and potentially tracing their movements, too. 

Experts say it's important to have a solid contact tracing system in place to keep the spread of COVID-19 in check once restrictions are loosened. The theory is that tracing helps contain the spread by warning everyone who was in contact with an infected person that they are at risk of having the virus, reducing the likelihood that they infect others.

Tracing record 'pretty opaque'

Tracing — like physical distancing — is a tool to prevent an infected person from infecting others, explained Dr. Andrew Morris, medical director of the antimicrobial stewardship program at the Sinai Health System and the University Health Network in Toronto.

Tracing the contacts of each new case quickly is essential to slowing the exponential spread of the disease, Morris said in an interview Monday. However, Ontario's record on COVID-19 tracing "has been pretty opaque to me," he said.   

"My biggest fear is that we could be totally set up for another surge," said Morris. He said he is concerned that the province is talking about relaxing restrictions "without having a clear understanding around surveillance and tracing." 

When the first wave of COVID-19 peaked in Ontario in mid-to late April, with nearly 4,000 new infections in a week, public health units struggled to trace all those contacts promptly.

The province's largest public health unit now says its contact tracing system is not far from hitting the province's benchmark for success. 

"There is a plan that is underway to get us to that point," said Dr. Eileen De Villa, Toronto's medical officer of health, during her briefing on Monday. "We are actually surprisingly quite close to it here in Toronto."

Some parts of the tracing process still need work, said De Villa, including getting complete information from labs quickly. "It is difficult to follow up with patients, for example, if we don't actually have a valid phone number."

Toronto Public Health has more than 400 staff and 35 volunteer medical students involved in contact tracing investigations. 

"Each investigator is able to complete on average at least one new case investigation each day," said Dr. Vinita Dubey, associate medical officer of health, in a statement. "We continue to scale up our response as the local situation evolves, with additional staff being redeployed and trained every day."

'Truly national approach'

There's a crucial need for a national strategy, said Premier Doug Ford. 

"We need a national plan for contact tracing," Ford said in an unscripted remark during his briefing Monday. While contact tracing is done by provincial public health units, Ford said he spoke Monday with Deputy Prime Minister Chrystia Freeland and indicated that a national plan "is absolutely critical."

Ford did not specify what such a plan would involve, and his staff did not provide any further details when asked. 

Ford and Freeland "discussed the importance of testing and contact tracing and the need to do more across the country. They also discussed the need for a truly national approach," said Freeland's press secretary, Katherine Cuplinskas, in a statement.

Federal officials say Ottawa's objective is to strengthen provinces' capacities for testing and tracing and to make sure best practices are shared.