COVID-19 testing, contact tracing key to fending off second wave, experts say

COVID-19 testing, contact tracing key to fending off second wave, experts say
Graham Hughes / The Canadian Press
Provinces have ramped up testing capacity in recent weeks, but disease experts say more robust testing is needed to avoid future outbreaks.

Provinces hit hardest by COVID-19 have ramped up testing capacity as they plan to reopen their economies, but infectious disease experts say there will be recurring outbreaks without more robust testing, contact tracing and quarantine services across the country.

A Canadian Press analysis of provincial data over a seven-week period starting in late March shows the provinces with the highest number of infections – British Columbia, Alberta, Ontario, Quebec and Nova Scotia – each faced their own unique epidemics, with different positivity and mortality rates based on the number of confirmed cases.

Those provinces also took different approaches to determining who to test and when, decisions that were at least partly influenced by their ability to scale up lab capacity as well as the resources some had available to do tests.

The rationing has become less prominent each week as availability of testing capacity has increased,” said Dr. Peter Phillips, a clinical professor in the division of infectious diseases at the University of British Columbia. “Testing is not easy to access like buying chewing gum across the country, but it’s a lot more accessible.”

Canada’s chief public health officer, Dr. Theresa Tam, has said reopening schools and businesses relies on testing and the ability of public health departments to trace the contacts of positive cases. Physical distancing also remains critical since people who aren’t experiencing symptoms can spread the disease.

More than a million people in Canada have been tested for the novel coronavirus, with over 61,000 positive tests as of Friday.

Alberta has been a testing front-runner with 3,950 tests completed per 100,000 people between Jan. 23, when testing began, and last Thursday. More than 174,300 tests in total were completed in the province to that point.

That province’s cumulative per capita testing is bested only by the Northwest Territories. The territory of just under 45,000 had completed the equivalent of 4,184 per 100,000 residents as of Thursday.

Ontario had completed more than 397,000 tests at the same point, which amounts to just under 2,700 tests per 100,000 people. However, in the last week Ontario surpassed Alberta’s number of daily tests per capita.

Alberta has still completed nearly six times the number of tests for every person who has died due to COVID-19 compared with Ontario – a measure Phillips said is useful to assess the extent of testing relative to the true size of the epidemic.

Nova Scotia had completed 3,462 tests per 100,000 residents as of Thursday, Quebec had done 3,173, and B.C. had conducted 2,054 tests per 100,000 people.

As of Friday, Quebec had 36,150 cases of COVID-19, Ontario 19,598, Alberta 6,098, B.C. 2,315 and Nova Scotia had 1,008.

Phillips said Quebec’s high proportion of positive tests is an indicator that significant transmission is still happening. As of Thursday, more than 13 per cent of the nearly 271,000 tests completed in Quebec yielded positive results.

By comparison, as many as one in four tests come back positive in the United Kingdom and New York, a proportion Phillips called “very disturbing.” Countries that are bringing the epidemic under control are seeing “very few of their tests coming back positive,” he said.

As public health restrictions are eased, Phillips said the provinces and territories must maintain a low threshold for testing in order to detect and isolate COVID-19 cases quickly and avoid large outbreaks and exponential growth in cases during a second wave.

To stop transmission, provinces will need to test “very liberally” to identify cases, and not just the symptomatic ones, he said.

Testing also goes hand in hand with contact tracing, which involves isolating and questioning each person who tests positive about any behaviour that might have caused the virus to spread.

“The contacts should be tested because that may identify other people, which will then trigger more contact tracing on those people who are testing positive,” said Phillips, adding that not all the provinces with a higher number of cases have taken that approach.

The extent to which people who are directed to self-isolate or enter quarantine are being monitored across Canada is also unclear, he said.

Other jurisdictions that are closer to the origin point of the virus in Wuhan, China, such as Hong Kong and Taiwan, have done better than Canada when it comes to keeping COVID-19 cases and fatalities at bay, said Phillips.

He attributes that success in no small part to contact tracing enhanced by mobile apps, which have sparked a privacy debate in Canada.

Phillips said COVID-19 moves too fast for conventional public health measures alone and privacy is not the only concern.

“What about the liberties of uninfected Canadians who are at substantial risk of dying here?” he asked.

Phillips also expressed concern that public health departments are underfunded and overloaded, especially in Ontario and Quebec, which are still reporting hundreds of new cases each day.

“COVID-19 is the biggest thing this country has had since 1918,” said Phillips, referring to the flu pandemic that killed at least 50 million people around the world. “And for strange reasons, the public health department, which is our main defence, doesn’t seem to be getting a big funding rescue package.”

A spokesperson for the Public Health Agency of Canada said it’s slated to receive $230 million of the $1.1 billion Ottawa has committed to public health measures in the wake of COVID-19.

The federal government also allocated $500 million to support the provinces and territories, but the Finance Department did not respond to questions about how much money is going to contact tracing and quarantine services.

The chief of the microbiology division of the Nova Scotia Health Authority agreed with Phillips, saying public health is one of the first places provinces have looked to cut spending over time.

“It takes a lot of human resources to do good old contact tracing,” said Dr. Todd Hatchette. “So if you don’t fund it appropriately, you’re not going to get the biggest bang for your buck.”

Here is a look at the approach to testing in British Columbia:

British Columbia

Although B.C.’s handling of the epidemic has garnered praise, the province has consistently been testing at a lower level than the other four hardest-hit provinces.

The Ministry of Health said in an email that labs have the capacity to complete around 6,500 tests per day, and 82 collection sites across B.C. are well stocked with supplies.

But last week, daily tests completed in B.C. ranged from around 1,800 to 2,800.

B.C. initially began testing symptomatic people who had travelled to areas of China affected by the novel coronavirus. In mid-March, the province expanded testing to include health-care workers, residents of long-term care facilities and hospital patients with respiratory symptoms, as well as people connected to a cluster or outbreak.

Starting April 8, clinicians could order COVID-19 tests, but daily testing didn’t increase until later in the month, when provincial health officer Dr. Bonnie Henry announced updated guidelines that emphasized testing anyone with new respiratory or COVID-19 compatible symptoms, however mild.

There were more than 15,230 tests completed in B.C. between April 4 and 17, and just under 29,630 in the following two weeks between April 18 and May 1.

The latest guidelines also prioritize testing for residents of remote or Indigenous communities, people living in congregate settings, such as work camps, correctional facilities and shelters, as well as people who are homeless and essential service providers.

Henry said there’s no specific number of tests that must be done each day, but it’s important to test the right people.

Phillips agreed there isn’t a magic number, but he said there’s increasing evidence that people who came into contact with a case should be tested even if they are not experiencing symptoms and regardless of whether they are connected to an outbreak.

“I suspect there could be more testing in B.C., for sure, and I think as we move towards opening up commerce and getting back to something closer to normal, the testing threshold should be kept low, so that we’re not missing any transmission in the community.”

The B.C. Centre for Disease Control says people who aren’t experiencing symptoms don’t require a test, even if they are a contact of a confirmed case or a returning traveller who is self-isolating at home.

Phillips said declining admissions to intensive care due to COVID-19 indicate the size of the epidemic in B.C. is smaller than it was several weeks ago.

Henry said B.C. plans to ramp up testing heading into the fall, when there will be more respiratory illness circulating, including influenza.

This report was initially published by the Canadian Press on May 11, 2020


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