Ottawa teeters on knife edge as COVID-19 cases mount, says epidemiologist
Still unclear whether city will see a second wave or whether new clusters will burn out
Ottawa is seeing a persistent rise in the number of confirmed COVID-19 cases, a sign that the city may be approaching a tipping point, says an epidemiologist who does infectious disease modelling for Ottawa Public Health.
Over the last two weeks, the city has had an average of about 21 new confirmed cases of COVID-19 a day. That's more than three times what the city saw in the two previous weeks, when the daily average was six cases.
"We're just on that knife edge," said Dr. Doug Manuel, senior scientist with the Ottawa Hospital.
Manuel's models in late May showed that if Ottawa residents reduced physical distancing by 20 per cent in June, the city could see a second wave of hospitalizations in September.
Based on the current rate of infection, Ottawa is approaching that number and may be in line for another surge, Manuel said Tuesday.
"We're in a growth phase," he said. "This has definitely caught everyone's attention."
Ottawa Public Health believes the new cases were primarily transmitted at large, indoor gatherings of younger people in private settings.
Manuel likens the clusters to small fires in a dry forest: through contact tracing, public health officials have an opportunity to stamp out the spread, so long as they look wide enough and catch all the sparks.
If people can't be traced — for instance, if guests lists are fuzzy and not all attendees can be found — they may end up spreading the virus, and soon there's a wildfire.
There's also the risk, Manuel said, that the clusters are simply the fires we know about, and there is wider community spread already happening.
"The question is whether it's isolated to those communities and they'll kind of burn themselves out or ... whether it's indicative of some challenge in physical distancing more broadly and we're going to see increased growth."
Threshold could be hit
For University of Ottawa mathematician Robert Smith? (the question mark is part of his name), Canadians may have already tip-toed too far into relaxation, and there may not be an option to go back.
"You only have to incrementally increase the risk level that people are taking, and then suddenly you've tripped a threshold and you've got a disaster on your hands," he said.
If the second wave rises, which Smith? thinks is all but inevitable, public health officials will have no option but to send society back into lockdown for an extended period of time.
"I suspect we're going to come in and out of these lockdowns many times throughout the next several years. In some sense we'll get better at it," he said.
Manuel has a different response in mind, should Ottawa's cases continue to rise.
He argues the March shutdown was necessary in part because testing was unavailable on a large scale and the city was still seeing a large number of travellers arriving with the virus.
Ottawa is in a different place now, Manuel said, and we can be smarter and more targeted about shutdowns.
"I think what we're trying to do now is operate in a pretty big middle space," he said.
Manuel said businesses where physical distancing rules are being upheld relatively well, like inside bars and restaurants, could perhaps remain open during a future lockdown.
The focus may be instead on places where physical distancing isn't happening, like large gatherings at homes.
"My sense is that businesses are actually taking this pretty seriously," he said. "Where we're currently seeing cases in Ottawa are private settings."
That said, Manuel noted if COVID-19 spreads everywhere like it has in places like Florida, the city will have no choice but to consider a shutdown similar to the one in March.