As lockdowns ease across Canada, we face case-by-case decisions about which activities are low risk and which aren’t worth the risk. In recent weeks, Quebec Premier François Legault and now Ontario Premier Doug Ford have berated sun-starved Canadians for enjoying the warm weather in public parks.
Critics have countered that studies find extremely low rates of outdoor transmission. One working paper from Japan estimated open-air environments are about 20 times safer than indoors. Another working paper found only a single case of outdoor transmission out of 7,324 transmissions studied.
Still, we obviously want to make decisions with the best available data. And a big new piece of data just came out of the US. Last week, the Centers for Disease Control (CDC), the leading US health agency for infectious diseases, released a dramatic downward revision to their estimate of COVID-19 fatality.
The CDC now expects that COVID-19 will be fatal in just 0.2 to 0.3 per cent of cases, only two to three times higher than seasonal flu mortality, which averages about 0.1 per cent. This revision is an order of magnitude lower than the CDC’s March 27 estimate of up to 3.4 per cent fatality, which the World Health Organization (WHO) was also estimating at the time the lockdowns were originally implemented across Canada.
Although the CDC’s revision suggests that COVID-19 is much less deadly than we feared when the lockdowns were implemented, in today’s politicized atmosphere it’s important to note that this kind of revision is completely normal in epidemiology. Even in their March report, the CDC flagged their estimate as provisional, meaning it would almost certainly be revised. As in every crisis, whether a health crisis or an economic crisis, new data is constantly emerging. Decisions must take into account almost day-to-day changes in what we know.
It is also important to note that, even with these lower revisions, the CDC still expects the virus will impose massive burdens on the healthcare system. They now expect 2.2% of those infected will require hospitalization; in Canada that could imply tens of thousands of additional hospitalizations on a system that is already stretched thin.
More broadly, what do these revisions mean for Canada? Though there are broad similarities between Canada and the U.S., ranging from demographics to age profile to economic and social patterns, still there are differences. The U.S. has about twice as many COVID-19 cases and deaths per capita as Canada. But the U.S. is also doing more virus testing, which could account for some of that difference.
Even so, differences inside the two countries massively outweigh the differences between them, with per capita cases running 20 times higher in Quebec than in British Columbia. There are similarly wide differences across US states. This suggests variation is greater locally than nationally. At the same time, in both countries national trends for both cases and deaths are similar, following familiar bell curves that suggest the worst may be over.
Beyond these aggregate estimates, to know the true risk to Canadians we need much more data, including seroprevalence testing that would establish how many Canadians have already had COVID-19 and recovered. Until such data is available, however, it’s hard to ignore a ten-fold downward revision in expected mortality.
Incidentally, those regional differences in Canada raise the question whether lockdowns are even hitting the mark at all. After all, if a policy used across Canada is yielding a 20-fold difference in death rates by province, perhaps other factors are more decisive. And when over 80 per cent of COVID-19 deaths in Canada are occurring in senior centres, it is possible that lockdowns targeting those of working age may hurt more people than they help, be it from depression, suicide, or delayed surgeries or cancer detection among the middle-aged. Interventions targeted to the elderly and to vulnerable populations might do more to save lives than preventing people from working or in fact going to the park.
Before coming down too hard on Canadians taking some well-deserved pleasure in difficult times, we should keep an open mind and understand that restrictions intended for the worst-case scenario may no longer be appropriate, given the emergence of new data.
Peter St. Onge est chercheur associé senior à l’IEDM. Il signe ce texte à titre personnel.