Vivek Goel is a professor at the University of Toronto’s Dalla Lana School of Public Health, and vice-president of the school’s research, innovation and strategic initiatives
As a public health physician, I get asked a lot of questions these days – I am more popular than I have ever been. I can answer many of the questions; some I can refer on to other experts. But there is one question neither I, nor anyone else, can truly answer: How long will this go on?
There are really two parts to this question. First, how long will we continue to see transmission of COVID-19? Second, how long will we see the most restrictive social measures on a global scale not seen in decades (or perhaps ever)?
For the first question, everyone is now familiar with the graphics from the U.S. Centers for Disease Control about flattening the curve. A tall and narrow peak is replaced by a smaller and wider peak. This figure has appeared everywhere in the last week. It is from the 2017 Community Mitigation Guidelines to Prevent Pandemic Influenza. The plan states “Specific goals for implementing NPIs [non-pharmaceutrical interventions] early in a pandemic include slowing acceleration of the number of cases in a community, reducing the peak number of cases during the pandemic and related health-care demands on hospitals and infrastructure, and decreasing overall cases and health effects.”
There are a few points to emphasize. We are aiming to slow acceleration, not completely stop COVID-19. We are trying to slow the rate at which the case count increases each day. It will still increase until we reach the new peak, but we hope not as quickly. Reducing the peak does not mean we won’t have a peak or that we won’t have many cases. The area under the curve, which represents the total number of cases, decreases, but not as much as the proportionate change in the height of the curve. The final part of that sentence is why we are doing this. The goal is to protect those most vulnerable to more severe disease and to help to ensure our health-care system can manage and support those individuals. Flattening the curve delays – but does not prevent – many of the cases in the community.
The vast majority of people who get this disease will have mild or no symptoms. They will likely develop natural immunity to the disease. As more people get the disease, herd immunity will develop, which means it will be less likely for the disease to transmit in the community and reach those who are most vulnerable to it. But flattening the curve means this will take longer. And the truth is, many of us will get COVID-19 and that will actually help bring things to an end.
Another point: The graphic is a hypothetical scenario. It is based on simulations based on assumptions derived from past experiences. No infectious-disease outbreak is the same as these previous ones. We are still learning about COVID-19, and it is fast becoming the most studied virus and disease in history. Yet there are still many basics we don’t fully understand, such as the true risk of transmission and the mortality rate. This is critical, as the assumptions that are made lead to wildly varying models of what the height of the curve will be. Furthermore, there is very limited experience in the modern era with the types of social-distancing measures being put in place. It becomes even more difficult to predict how much the curve will be flattened.
So how long do the measures have to be in place? It is impossible to predict, since we are in uncharted territory. As difficult as the decisions to impose these measures were, the decisions as to when to lift them will be even more difficult. I do not envy the task of those sitting in emergency-operations centres examining each day’s data telling them what happened in the community two weeks ago, and trying to divine whether we are past the peak. There will continue to be cases for a long time to come, in Canada and elsewhere in the world. Given the panic and fear now gripping our communities, it will be difficult to lift these measures while numbers continue to rise.
We will need to balance the worry about being infected with COVID-19 individually, or having it re-introduced into our communities, with the very pressing need to restore our society and economy.
Yes, it will take longer to flatten the curve over time, rather than to see it spike in a shorter period – but by doing so, we should save far more lives and the health-care system will be less strained.
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