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Rise in untraced COVID-19 cases puts Alberta response at risk, infectious diseases expert warns

Two-thirds of the COVID-19 cases most recently reported in Alberta have no known source.

'It makes it very difficult for us to have an accurate picture of where the virus is spreading'

Cases of COVID-19 with an unknown origin now dominate Alberta's case load. (Paul Chiasson/The Canadian Press)

​The growing number of COVID-19 cases in the province without a known source of infection means the virus could be spreading through Alberta communities unchecked, an infectious diseases specialist warns.

"It dramatically lowers the efficiency of contact tracing," said Craig Jenne, an associate professor at the University of Calgary in the department of microbiology, immunology and infectious diseases. 

"If we don't know where you got it, it's difficult to notify other people who also may have been exposed." 

Not only are the higher rates making the virus more difficult to track, it will make it more difficult to identify which restrictions would be most effective in controlling it, Jenne said. 

The numbers should serve as a wake-up call to Albertans, he said. 

"It makes it very difficult for us to have an accurate picture of where the virus is spreading in the community. What are the sources that are driving this? These are big problems." 

Currently the source of two-thirds of the COVID-19 cases in Alberta is unknown.

Of the 3,768 new cases reported in Alberta between Oct. 27 and Nov. 2, the source of infection could not yet be identified in 2,548 — 67 per cent of cases, a percentage that is rising. 

In mid-October, 43 per cent of Alberta's newly-confirmed cases had an unknown source, with 37 per cent of active cases having an unknown source. 

But Dr. Deena Hinshaw, the province's chief medical officer of health, has said the true percentage of unsolved cases is closer to 50 per cent.

Rate concerning, Hinshaw says

During a news conference Wednesday, Hinshaw said the rate of unknown transmissions is concerning but the data should be examined with caution. 

Newly-reported cases have yet to be investigated, Hinshaw said. The number of unsolved cases could shrink from 67 per cent as contact tracers begin investigating each case in earnest, she said. 

For example, of the 6,110 active cases in the province Tuesday, only 53 per cent were of unknown origin.

"Because the volume of cases we're seeing every day has been rising, and when we get a new case, an investigation has yet to take place," Hinshaw said. 

"Many of those cases, we will be able to determine the source."

Health Minister Tyler Shandro told reporters Wednesday the proportion isn't a concern. 

"It's just a matter of people getting their tests before the contact tracers have spoken to them," Shandro said. 

The increasing rate of unknown cases comes at critical time with more people in hospital and in ICU for the disease than ever.

'Critical juncture'

Adjusted for population, Alberta now has the second-highest number of active COVID-19 cases of all provinces.

Hinshaw has said the province is at a "critical juncture" in its bid to reverse the trend and suggested that a growing carelessness around COVID restrictions could exacerbate the problem. 

While health officials can't pinpoint the source of all the new cases, there is a clear trend behind the spike in new transmissions, Hinshaw said. 

"We do know what the trends are in our own data and those trends match the transmission issues that we're seeing in other provinces, which are social gatherings," she said. 

"They are times when people are spending time together in close contact, not wearing masks, not distancing, not staying home when they're symptomatic, and those are the things we're really focused on." 

Hinshaw warned if efforts to reverse the trend through voluntary measures fail, further restrictions could be imposed and soon.

"We'll be watching very closely over the coming days to see if we've been able to start turning the corner with our current restrictions or if more restrictions are necessary." 

Meanwhile, Alberta Health and the province are promising to reverse the trend by speeding up test turnaround times and bolstering its team of contact tracers. The contact tracing team, a workforce which has already doubled in size since the pandemic hit, will expand again.

More contact tracers on the way

Alberta's staff of disease detectives will grow from 800 to 1,100 within the next few weeks.

"We are working to reduce the number of unknown cases as soon as possible," Alberta Health spokesperson Tom McMillan said in a statement. 

"This is primarily being done by reducing wait times for testing and test results and speeding up contact tracing," McMillan said. "We have seen wait times lower in recent days as a result of shifts to our strategy and AHS is hiring more contact tracers to expand their dedicated teams." 

Contact tracing is a laborious but critical step in slowing the spread of the virus. Once a person tests positive for COVID, a public health team begins the work of tracking their movements and close contacts.

"These folks are working, like all of our public health folks, working really long hours," Shandro said.

Those who may have been infected are informed, tested and often asked to quarantine. The process can involve a few simple phone calls or be complex and protracted, depending on how many people the infected person has come in contact with. 

"The system is working seven days a week," Shandro said.

"If I could speak on behalf of our contact tracers, they wish that Albertans could follow the public health guidance so there would be less pressure on them but it's also why we're continuing to hire contact tracers." 

'No excuse' 

Jenne said increasing the number of contact tracers and faster testing will help. The job of contact tracers has become more difficult in recent months, he said.  

"These are big problems, but they're also suggesting that people are perhaps having too many contacts in the community. 

"What is perhaps even more disturbing is we are seeing increased reports of people not being forthcoming with their known contacts as well." 

Even so, the success of Alberta's fight against COVID-19 will hinge largely on individual decisions, Jenne said. 

"COVID fatigue, it's real and it's understandable," he said. "But it's also not an excuse. 

"We have to do what we can now to not put ourselves in a situation where the public health officials have no option but to bring in restrictions."

About the Author

Wallis Snowdon

Journalist

Wallis Snowdon is a digital journalist with CBC Edmonton. She has nearly a decade of experience reporting behind her. Originally from New Brunswick, her journalism career has taken her from Nova Scotia to Fort McMurray. Share your stories with Wallis at wallis.snowdon@cbc.ca

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