‘Definitive increase’: Experts warn of underestimating recent increase in COVID-19 cases


CALGARY – Infectious disease specialists say a recent surge in COVID-19 cases that surpassed a peak last spring shouldn’t be ignored as simply a by-product of increased testing. “I think minimizing right now is a real mistake,” said Dr. Lynora Saxinger of the University of Alberta.

“People don’t want to believe it’s a thing, because I think they don’t want to go back to the state we were in earlier this year. It is a dangerous path to take and we should be much more careful. now. ”

The Canadian Press compiled data published in Alberta, British Columbia, Ontario and Quebec for a week ending April 21 and another ending October 6 to get a feel for the comparison between the two cases.

Daily cases in Alberta were two percent higher in the most recent period compared to the week of April. Ontario cases were 13 percent higher, Quebec’s were 14 percent higher and British Columbia’s cases were more than triple the low double-digit average number recorded in April.

Alberta, one of the early leaders in increased testing, took nearly four times more samples during the week of October than during the week of April. British Columbia’s daily tests were up eightfold, while Ontario and Quebec took about 4-1 / 2 times more weekly samples during the fall week than in the spring.

The positivity rate – the percentage of tests that come back positive – in all four provinces fell markedly between the spring and fall outbreaks.

Quebec and Ontario do not officially publish historical positivity rates, which is why the Canadian Press divided the total number of weekly tests by the total number of weekly cases. This is an imperfect estimate because there is often a time lag between when tests are done and cases are registered by public health.

Quebec, which performed an average of about 6,300 daily tests and 930 new cases during the week of April, had a positivity rate during that period of about 15%.

In the most recent week, as Quebec has experienced five straight days with new four-digit cases, its positivity rate was around four percent.

Ontario, which faces a large backlog of samples awaiting analysis, posted an official daily positivity rate of 2% for October 7, down from the range of about 6% that he had in mid-April.

Alberta’s positivity rate fell from nearly 5% to one percent and that of British Columbia fell to 1.3 percent from four percent.

Experts say the lower positivity rates shouldn’t be any comfort.

Early testing was largely limited to people with a handful of specific symptoms and those who had close contact with them. The tests are now available for a much larger part of the population and many other mildly symptomatic or asymptomatic cases are being discovered.

“The threshold for what we consider a high positivity percentage should probably be viewed as different now than it was in the spring,” Saxinger said.

Dr. Craig Jenne, an infectious disease researcher at the University of Calgary, noted that testing of people without suspected exposure or symptoms in Alberta over the summer has uncovered very few new cases. The province has since tightened its asymptomatic screening criteria, restricting them to those at higher risk or who need to travel ahead.

“We are still screening asymptomatic people, but these are people who we have reason to believe have been exposed and who seem to capture most of the cases in the community,” he said.

Jenne recalled that the numbers we see today reflect the viral transmission that occurred 10-14 days ago.

“So we always have to react to what is happening and not necessarily what is happening today. ”

In recent weeks, testing has been relatively stable as cases have trended upwards.

“There has been a marked increase in the number of people infected. It’s not just because they test more, ”said Dr. Ameeta Singh, infectious disease specialist at the Royal Alexandra Hospital in Edmonton and the University of Alberta.

Hospitalization trends are a lagging indicator that experts watch with concern.

In Ontario, for example, hospitalizations started climbing triple digits about two weeks ago and as of Friday 225 people were hospitalized.

“This is definitely where we start to get a little more alarmed,” Singh said.

“It’s kind of the tip of the iceberg. This tells you that there is much more community transmission than you might think. ”

This report by The Canadian Press was first published on October 9, 2020


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