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COVID-19: How do we make sense of the modelling?

The biggest question on everyone’s mind right now is: “When will this pandemic be over?"

Jo Snyder


Unfortunately, we don’t have a clear answer to that question right now, and modelling isn’t a crystal ball with the answers inside.


Canada’s Chief Public Health Officer, Dr. Theresa Tam, assures us, though, that models do “help us to plan and they tell us that our collective actions can have a direct and significant impact on the epidemic trajectory.” And since modelling is guiding our national response to the COVID-19 pandemic, you might find it helpful to understand why.


What is modelling and why is it important?


The kind of modelling we’re talking about here is done by epidemiologists studying the instance and trajectory of how diseases move through populations. Projections are made via data collected from the global experience of COVID-19 as well as what has already happened here in Canada.


Critics of this type of modelling feel like we’re risking too much freedom on an inexact science. But Robert Smith, a disease modelling professor at the University of Ottawa, reminds us that it’s not a matter of if we get the virus, but when.


So, understanding the worst-case scenario, meaning if we do nothing and let the virus rip through our communities, and acting on how to prevent that scenario, keeps our hospital ICUs from becoming overwhelmed. And we’ve seen in Italy and New York City what overwhelmed looks like. Devastating. 


Modelling isn't exactly right, but that doesn't make it wrong


Disease modelling uses public health information to predict outcomes and, like all predictions, sometimes the outcome isn’t what we had in mind. You might be thinking if we don’t have an apocalyptic outbreak that kills more than 200,000 Canadians, then maybe the models were way off and we were lied to (shakes fist).


But that’s not necessarily the conclusion. This is because we are dealing with potential scenarios, not exact predictions. Models use the best data available at that particular time; the challenge with COVID-19 is that the data is changing daily.


Modelling helps us plan


“In the early days of an epidemic it’s all about providing an important early steer to policy-makers, about what they should be doing,” said Dr. Peter Donnelly. Otherwise, we essentially operate blindly without any information and insight at all.


It’s hard for policymakers to make big moves, like asking a country to shelter in place, without some kind of data, worst-case scenarios, and the scope of the problem. Models help them see that. And they’re sharing what they’re seeing with us, the public.


Modelling affirms that our personal actions can make a difference


University of Toronto epidemiology professor Ashleigh Tuite says that “We’re in a situation where we need buy-in from everybody”. Right now, she says, if everyone has the same information then we can have the same conversation about the best course of action to reduce the number of fatalities from COVID-19.


The best-case scenario projections for Canada should encourage us to stay the course of sheltering in place. It shows us that our efforts can and will make a difference.


Dig into the reading


Dive into some more reading about modelling if you’re so inclined, but don’t lose the plot of what we’re doing here. Across Canada we want to flatten the epidemic curve together by staying home as much as possible, practising physical distancing at all times when you’re out, and washing your hands.


Jo Snyder is a seasoned communications professional with expertise on the social determinants of health and health equity. Over her career, she's worked with think tanks, non-profits and big tech to deliver comms of all kinds.


This project has been made possible in part by the Government of Canada.

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