Pandemic detectives: How Manitoba does the crucial public health sleuthing to contain COVID-19

Walking past it, you might not guess the low brick building on the edge of Winnipeg's Exchange District is a hub of one of public health's most critical tools in containing the spread of COVID-19.

Inside, lined up at desks spaced two metres apart, a team of public health nurses make dozens of phone calls a day, to every person in the region sick with the disease caused by the new coronavirus, and every close contact of each of those cases.

They're doing contact tracing, the time-consuming public health detective work of tracking the past movements of people who have COVID-19 to figure out how they got it and who they might have given it to.

"It's very important because it's the opportunity that we have to quickly identify [illness]," said Dr. Bunmi Fatoye, medical officer of health with the Winnipeg Regional Health Authority and the expert in charge of contact tracing efforts in the region.

Leaders across Canada and the world have said aggressive contact tracing is a crucial element, alongside testing, in the public health fight against COVID-19.

In Manitoba, the contact tracing team has already been dramatically scaled up. The usual team of six public health nurses has increased to as many as 50 depending on the need, said a spokesperson for the Winnipeg Regional Health Authority.

"That's a million-dollar question," said Fatoye, asked how many people are working on contact tracing in the province at any given time. "Everybody, all hands on deck is the answer."

In the U.S., the Johns Hopkins Bloomberg School of Public Health estimated as many as 100,000 people may be needed to do contact tracing. A former head of the U.S. Centers for Disease Control has said it could be as high as 300,000.

In Canada, a call from the federal government for volunteers at the beginning of April included an ask for people who can help with contact tracing, as well as tasks like data collection.

"As we get this first wave under control, the absolute key is to have sensitive systems to detect any new cases and then to do rigorous contact tracing around those cases," said Dr. Theresa Tam, Canada's chief public health officer, in a news conference earlier this month.

'A need to know more and more'

Contact tracing was already well-established in Manitoba prior to the pandemic, tackling contagious maladies from tuberculosis to sexually transmitted infections. But COVID-19 posed a challenge no contact tracers in the world had faced before, and brought with it demands for ever more detail, knowledge and speed.

"The difference is the novelty of the disease and the fact that there was a need to know more and more," Fatoye said.

"The contact tracing needed to be more rigorous, needed to be very complete, so that we can have data to analyze, and hopefully inform the next steps and add more information."

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Not all contact tracing is happening out of the centre on Hargrave Street, she added. Other nurses are working out in the community as well, she said.

When a case of COVID-19 is identified, public health nurses begin by calling the patient and doing an initial interview, Fatoye said. In the early days of the pandemic, as staff first learned about the disease, that first interview could take as long as two hours, she said.

They begin by asking questions to verify the patient is who they say they are. From there, they dig into how the person got sick with questions about recent travel and possible exposures, Fatoye said. 

After that, they ask the patient about symptoms — what they're experiencing and when it started.

The timing of the symptom onset is key. It's the crucial nugget of information the team needs to figure out when the patient became infectious to others — the "period of communicability" — and shapes ensuing efforts to notify possible contacts.

'There was panic'

In Manitoba, public health officials define the period of communicability as beginning two days before symptoms began.

Once that's been identified, nurses ask the patient to dig through their memory to sort out where they went and who they saw in that time. Nurses begin with open-ended questions, Fatoye said, but also use more targeted prompts to help patients who are struggling to remember.

"Then we go day by day, and so we walk them [through]," she said. "Yesterday, what did you do? What did you do the day prior? Kind of walk it backward."

They're looking for close contacts of patients during the period of communicability. In Manitoba, that means someone who was within two metres of them for longer than 10 minutes, although not all jurisdictions define it the same way. 

New Brunswick, for example, focuses on exposures lasting longer than 15 to 30 minutes.

When they find those contacts, they start phoning them up, too.

Every day, nurses from the contact tracing team call each and every confirmed case of COVID-19 in the region to check in on them and their symptoms, as well as all the possible contacts.

"Initially, we had lots of work just to interview the case, just to get the contacts," Fatoye said. "There was so much going on out there in the environment. People were anxious, there was fear, there was panic."

'Moment of shock'

Contact tracing is highly reliant on patients' memories, Fatoye said. One of its limitations is that if a patient doesn't identify a certain person as a contact, the nurse can't know to alert the individual.

"We really rely on them to tell us as much as possible," she said.

But memory's not perfect. Sometimes, patients call back after a phone call because they got a date wrong, Fatoye said — especially in the initial phone call right after someone finds out they're sick.

"Sometimes people are in that moment of shock," she said.

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Tracing a contact's history has become easier and faster as the disease becomes more familiar, Fatoye said. Early in the outbreak, information about the illness was constantly changing, she said, and nurses had to keep up.

The number of new confirmed cases in Manitoba has been relatively low in recent days, and the number of contacts for each case has dropped, too, she said. Fatoye credits that to the early closures of many businesses and schools, plus limits on large gatherings.

Early in the outbreak, cases had an average of roughly nine contacts each, she said. Now, it's more like three.

Contact tracing app not being considered: spokesperson

As Manitoba and jurisdictions across the country begin conversations about how to reopen the economy, leaders have said expanded testing and contact tracing will be crucial.

Leaders are already turning their attention to how to increase contact tracing, including at least two provinces — Ontario and British Columbia — which are pursuing vendors for apps to help track contacts digitally.

Ideas include apps that would ask for users' permission to track and share their anonymized GPS data, or that assess users' risk factors for COVID-19.

A spokesperson for the Winnipeg Regional Health Authority says that's not currently being considered in Manitoba.

In Manitoba, Premier Brian Pallister has already said he wants to see the province processing up to 2,000 tests per day at the Cadham Provincial Laboratory in order to reopen the economy.

As testing expands, more confirmed cases will mean more contact tracing. On Thursday, Dr. Brent Roussin, the province's chief provincial public health officer, said he believes the province can scale up as needed.

"Certainly we should be looking to have the capacity to test that many people. Certainly it's going to rely on the demand," he said. "But certainly we would be in a position to do the contact tracing and follow up on cases at this point."

For now, Fatoye says the workload is "much more manageable" than it was in the early days of the pandemic.

She urged Manitobans to keep it that way, by continuing to follow public health rules and recommendations.

"Keep doing the hand-washing. Keep practising … physical distancing," she said. "Because at the end of the day, it's still what is going to help reduce that spread."