Severe restrictions on public life must continue for months, not weeks, for Ontario to stifle the coming surge of COVID-19 patients and give the health-care system a shot at coping with the pandemic, University of Toronto-led research suggests.

Outbreak modelling shows that four weeks of intensive social distancing interventions will be insufficient to suppress a sharp rise in new cases, hospitalizations, and critically ill patients in intensive care.

The disruptive measures must continue for more than six months to slash the size of the epidemic peak by more than half and delay it long enough that a vaccine might become available, the model found.

The researchers, a team led by Ashleigh Tuite of U of T, readily acknowledge this is a policy “nightmare” and recognize the extreme hardship that even a few days of social distancing has already inflicted.

The modelling work has not been peer-reviewed, and the exact numbers should be interpreted with caution. But the team’s research echoes that of scientists at Imperial College London, which found that extreme social restrictions might need to last 18 months in the U.S. and U.K. to avert hundreds of thousands of deaths.

“The honest answer to that is this is going to be a while,” Tuite said Wednesday.

“We’re not going to back to normal life in two weeks or four weeks.”

The model uses data on disease outcomes from China, where the COVID-19 outbreak was first detected, matched with Ontario’s population size and age structure.

In a scenario with no interventions, Ontario will see upwards of 140,000 new cases at the peak of the epidemic, 100,000 patients in hospital and 56,000 people in intensive care, the model found. This surge would crash into the province about three months from the start of the outbreak.

This scenario will not occur. The province is already undertaking social distancing initiatives, by closing schools, daycares and public facilities and encouraging everyone who can work from home to do so. But it represents a baseline from which to measure the effect of different interventions.

Even though the no-intervention scenario won’t happen, it shows why severe social distancing is so important: 56,000 patients is more than 20 times the number of ICU beds in Ontario, even with the added capacity the province is scrambling to create.

When the researchers modelled the effect of lifting social distancing after four weeks, letting everyone return to work and school, the peak of the epidemic would still overwhelm the province’s health-care system: new cases fall by a quarter, and ICU patients drop by one-fifth. The peak of the outbreak in this scenario is delayed by only seven weeks.

Even eight-week and 16-week interventions weren’t enough to cut the surge of patients, hospitalizations and ICU admissions by half, or shift the peak of the epidemic by more than a couple of months, the researchers found.

With 32 weeks of social distancing interventions — about seven and a half months — the peak of the epidemic is pushed out by more than a year, which is the earliest possible timeline for the creation of a new vaccine, though there are no guarantees one would be ready by then. In this scenario, new cases, hospitalizations and ICU patients were cut down by more than two-thirds at the epidemic peak — still far too many for Ontario’s current health-care system, but it buys time to expand.

In all of these scenarios, the researchers found the same number of people become infected overall. But slowing down how quickly the virus rips through society and flattening the peak of the outbreak gives hospitals a chance to properly treat patients, improving survival rates.

“If we decide we want to flatten the curve, and have this be a slower and more controlled outbreak, it means that we’re talking about long periods of disruption,” said Tuite.

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“I’m an epidemiologist … I’m not a policy person. I don’t know how on earth you do this,” she said. “Honestly, it just scares me. I see this, and I’m talking to people who don’t have jobs or are out of work. We can’t do a year of this. I don’t know.”

“I am in agreement that four weeks isn’t enough,” said Jane Heffernan, a professor of mathematics and statistics at York University and communications director for York’s Centre for Disease Modelling. Heffernan was not involved in the U of T research.

Her own research has also indicated that longer interventions are necessary. Heffernan is working on modelling what happens when compliance wanes — it is very difficult for entire populations, and especially for children, to continue severe social restrictions over a long period.

The findings are in tune with those of a high-profile report from a modelling group at Imperial College London. That group found trying to mitigate the effects of the pandemic in the U.K. and U.S. would still result in hospitals, especially intensive care units, being “overwhelmed many times over,” and hundreds of thousands of deaths.

So they also modelled a strategy of suppression: maintaining social distancing restrictions and other containment interventions over a long period of time. It curtailed the worst outcomes, but suppression has to be continued until a vaccine becomes available, which could be 12 to 18 months out.

“We predict that transmission will quickly rebound if interventions are relaxed,” the authors wrote.

Restrictions four weeks from now wouldn’t necessarily look the way they do today. The Imperial College group modelled a scenario where social distancing and other containment interventions are cycled on and off — though the practicality of that for schools and businesses is unclear.

Tuite agreed. “If we want to get through this, that sort of reactive, up-and-down responding to what we see is probably the most sustainable approach.” But it will likely involve trial and error, she added: “I think we need to acknowledge that we don’t know what we’re doing, and we don’t know what’s going to happen.”

Heffernan urged that with across-the-board compliance for social distancing — everyone limiting all but the absolutely necessary social contacts outside the home — restrictions might not have to last quite so long.

“I want (readers) to walk away thinking about how their behaviour matters. Every person matters and in order to protect everybody, we all really need to be diligent in keeping our social distancing behaviour up until we know that it’s safe to bring it down.”

The actual behaviour of the outbreak in Ontario could be better or worse than the research suggests. Scientists are hoping that warm weather dampens the infectiousness of the coronavirus, though there isn’t strong evidence for that yet.

“I’m very, very happy to be totally wrong here,” Tuite said.

Correction - March 20, 2020: This article was edited from a previous version that included an incorrect reference to the number of intensive care patients that would have to be treated as 58,000. In fact, as stated earlier in the article, the model estimates that Ontario will see 56,000 people in intensive care if there was no interventions.