COVID-19: a Canadian study models the impact of the end of social distancing

Australia will slash the number of returning citizens allowed into the country by half as it struggles to contain a worsening coronavirus outbreak in its second-largest city Melbourne.

Canadian researchers have developed a mathematical model of the effectiveness of social distancing in controlling the COVID-19 epidemic in Ontario. They predict that a radical lifting of these precautionary measures in the province, without parallel screening tests or other compensatory measures, could saturate hospital services within a month. 

In Europe and elsewhere around the world, countries are gradually emerging from lockdown. But to what extent is it possible reopen parks and restaurants and return to normal life without risking a second wave of contagion? Canadian researchers have analyzed the different possible scenarios. 

Published on May 27 in the Annals of Internal Medicine, the conclusions of the study conducted in Ontario suggests that the lifting of all social-distancing measures in the coming weeks would lead to a rapid resurgence of the virus that would saturate intensive care services in the province within a month.

The prediction, developed by Population Medicine Professor Amy Greer at the University of Guelph and researchers at the University of Toronto, Canada, is based on a mathematical model created in the early spring, which took into account the number of of COVID-19-infected patients in intensive care in Ontario between March 19 and May 3, and the death rate among these patients. 

The new study presents a revised version of this model, which has now been adjusted to reflect events that transpired following its creation. "This paper goes back, uses the same model, but updates it by calibrating it with observed Ontario data as well as data on what we now know about the biology of the disease," explains Professor Greer. 

Five times the number of deaths without social distancing

According to the new study, the province of Ontario would have had five times as many deaths without social-distancing measures introduced in mid-March. Deaths among hospitalized patients without the intervention were estimated at 12.7 deaths per 100,000, compared to 2.5 deaths per 100,000 with social distancing. 

The research team also examined the time it would take to exceed the available number of intensive care unit (ICU) beds in the province if social distancing was relaxed without any other compensatory measures. Assuming that social distancing reduced contact in Ontario by 70%, the study predicts that hospitals would be overwhelmed in just 35 days without it. 

Even if current restrictions remain in force until mid-June, the researchers also found that a subsequent abandonment of all social-distancing measures would lead to the health system being overwhelmed in just 41 days.

"The amount of contact that happens as we begin to relax is a major factor for determining how quickly ICU capacity is exceeded," points out Professor Greer, who goes on to conclude: "If we let up on physical distancing without concurrent increases in testing and tracing, there will be a rapid return to exponential growth."

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