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How contact tracing can help slow the spread of the coronavirus

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Written by Paul Taylor

Question: I volunteered to be a contact tracer of people diagnosed with COVID-19. But Toronto Public Health told me that I had to do the work in one of their offices, using their computers and phones. It seems risky going to a public place. Why can’t I do this work from the safety of my own home?

Answer:  When it comes to integrating volunteers into the daily operations of Toronto Public Health, officials are still grappling with the issue of how to safeguard patients’ personal health data.

Dr. Vinita Dubey, Associate Medical Officer of Health, explained in an email that “volunteers currently cannot work from home as they do not have remote access to the City of Toronto secure systems.”

But, she added, “we are investigating how people can volunteer remotely.”

Indeed, public health officials are looking for ways to ramp up contact tracing which is considered a critical tool for curbing the transmission of the novel coronavirus that causes COVID-19.

Contact tracing can be extremely labour intensive and it’s often compared to detective work.

As part of this task, public health staff interviews people who have been recently diagnosed with COVID-19. The patients are asked a series of detailed questions to determine where they might have picked up the virus, with whom they have been in contact, and if they might potentially spread it to others.

Then staff will follow up with those who might be at risk of exposure from the newly-identified case. Each person is told to remain in self-isolation for at least 14 days and to watch for potential symptoms of the illness.

“Whenever you have an infectious disease, you want to find the source and do everything you can to isolate the source from causing further infections,” says Dr. Andrew Morris, medical director of the antimicrobial stewardship program at the Sinai Health System and the University Health Network in Toronto.

“If you can do that with everyone who has the virus, then you can halt the disease process in its tracks.”

But COVID-19 presents unique challenges because some infected individuals appear to be capable of transmitting the virus even though they have no obvious or very minimal symptoms such as a cough or fever. That means they may be out in the community and unknowingly spreading it around.

To make matters worse, medical researchers are only beginning to unravel the mysteries of the novel coronavirus, officially called SARS-CoV-2.

“We still don’t know the precise time during which you are contagious,” says Dr. Nisha Andany, an infectious-diseases specialist at Sunnybrook Health Sciences Centre in Toronto.

If some people can transmit the virus before they exhibit symptoms, that further complicates the job of contact tracers.

“It’s unclear how many days you have to go back, in terms of figuring out where they were and who they came into contact with, before symptoms developed,” she adds.

“Do you retrace their footsteps a week or two before they developed symptoms, or is one or two days sufficient? Or, do you focus only the symptomatic period, even though we have reports of asymptomatic and pre-symptomatic transmission?”

But what can be said with some certainty is that contact tracing is most effective when it is done as quickly as possible.

The responsibility of doing this work rests with the local public health units. They have the legal authority to insist that people remain in self-isolation and they can reach out to others who may be vulnerable to infection.

However, contact tracers aren’t necessarily the first health-care workers to be in touch with people after a test confirms they have the virus. Instead, a physician connected to a hospital or a COVID-19 assessment centre may be the one to inform them of their positive test results.

Dr. Janine McCready, an infectious-diseases specialist at Michael Garron Hospital in Toronto, is concerned that valuable time is lost between when a lab confirms a positive test result and the contact tracer phones the individual.

So, when patients test positive at her hospital’s COVID-19 assessment centre, she goes a bit further than simply notifying them of the results.

“I ask them who their contacts are and who is in their household, and then I ask them to reach out to those people,” says Dr. McCready. She encourages infected patients to urge their close contacts to self-isolate as well.

But, of course, public health staffers – and not Dr. McCready – have the authority to directly phone the contacts. “I’m relying on people to follow through on their own,” she adds.

Other infectious-diseases doctors have also learned about potentially troubling situations when they call patients who’ve tested positive for the virus.

“In those cases, I will directly contact Toronto Public Health myself, asking them to follow up with a case sooner rather than later,” says Dr. Andany.

Toronto Public Health currently has over 500 staff and 45 volunteers (many of them medical students) working on case investigations and contact tracing.

“On average, it can take approximately one day to complete a new case,” says Dr. Dubey.

But some experts are worried that contract tracing will become much harder when the economy opens up again and the lock-down recommendations are relaxed.

“If you become infected and you were at a family dinner, then we need to speak to every family member and find out who they were in contact with because the concentric circles (of potential infection) span out from the first case,” says Dr. Morris.

He also notes that contract tracing involves more than just asking questions. “It’s educating people and creating behaviour change,” says Dr. Morris. Infected individuals need to know how to properly self-isolate and the best way to safeguard others. “That takes a lot of work.”

Toronto Public Health, well aware of these additional demands, is preparing for what might lie ahead. “We continue to scale up our response as the local situation evolves, with plans to redeploy and train additional staff in the coming weeks,” says Dr. Dubey.

Another challenge is that people may not accurately remember where they have been – or the time they were in specific locations. For that reason, some jurisdictions have been promoting smart-phone apps that track people’s movements.

Alberta, for instance, is encouraging its residents to use an app that will help identify those who have been in close proximity to an infected person. But the voluntary program has run into some resistance.

“Every place that electronic surveillance is being proposed, there are concerns around privacy and ownership of data – and understandably so,” says Dr. Morris.

“If you’re in an authoritarian regime like China you can get away with a lot more stuff than you can in somewhat libertarian North America,” he adds.

But even if contact tracing could pinpoint everyone who should self-isolate, it’s unlikely to completely stop all transmissions of the virus.

“For people with young kids or who can’t isolate, it becomes very difficult to prevent it from spreading within the household,” says Dr. McCready.

Most experts generally agree that multiple measures are needed to keep the virus in check.

Widespread testing, in particular, can help shine a spotlight on areas where new cases are surging so that public resources can be directed to vulnerable populations.

Furthermore, everyone should continue with personal protective precautions including wearing masks, frequent hand washing and physical distancing.

Essentially, we must assume that anyone we encounter could be harbouring the virus. So, when in public, stay at least two metres apart – and hopefully you will be out of reach of the viral particles which are spread through the tiny respiratory droplets from coughing, sneezing and possibly just talking.

About the author

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Paul Taylor

Paul Taylor, Sunnybrook’s Patient Navigation Advisor, provides advice and answers questions from patients and their families, relying heavily on medical and health experts. Email your questions to AskPaul@sunnybrook.ca
and follow me on Twitter @epaultaylor