Making sense of the statistics in the middle of a pandemic
How do we know if we are winning?
As spring hints at making its entrance, what should Saskatchewanians look for as signs that the province is winning or losing the battle against COVID-19?
Don't be alarmed if the numbers grow rapidly for a week or two. That may simply be the result of more widespread testing.
It will be more worrisome if the new cases cluster in the older population or in others at risk, in which case hospitalizations and deaths will rise, and the health care system could be seriously stretched.
The world is five months into the COVID-19 pandemic. Saskatchewan is a relative newcomer to the scene, with its first case confirmed on March 11.
Pandemics, especially those due to novel viruses, are among other things plagues of uncertainty. What is the real infection rate? What is the real fatality rate? How long will it last? Will it come and go and be done with as a major threat to health, or is this the dawn of a new era where the infections come in waves?
Globally, success may not be uniform. Battles won may not assure victory in the war.
Numbers may not tell the whole story
As of March 30, Saskatchewan had 176 cases and two deaths. Pay little attention to the first number.
There are not enough test kits to do mass screening, so people with symptoms or who have known contact with carriers get tested first. But 80 per cent or more of infected people experience no or mild symptoms. No jurisdiction knows how many are out there.
Alberta has the highest testing rate in the country, but it's still just one per cent of the population. Saskatchewan's rate is a bit lower. There could be two or three or 100 undetected cases for every confirmed case.
The second number – the two deaths – is low, but it will inevitably change. The question is by how much. It's extremely hard to predict.
As the graph below shows, fatality rates are (literally) all over the map, 20 to 25 times higher in the worst-affected countries than the least. Remember, though, that these are percentages of confirmed cases, not percentages of the numbers infected, which are unquestionably much larger, meaning the fatality rates are unknown but lower.
The differences between countries are real, even if they turn out to be somewhat exaggerated. There is a tendency to assume that the countries with low rates are doing something right and those with higher rates have dropped the ball. It may turn out that this is true, but it may also be luck. The differences may shrink over time as the pandemic peaks and eventually concludes.
I live in Melbourne and I am grateful for Australia's thus-far low case fatality rate. I can assure you that none of this good fortune is plausibly attributable to brilliant and far-sighted government leadership or a population that reliably does what it's told.
The one risk factor we know to be critical is age. It is shocking and tragic when a young and healthy person dies from the virus — and it has happened — but it's not common.
Still early days
The big debate is whether the virus is ultimately containable. The provisional answer is yes, in at least some places. China, the country of origin and hence ahead of the curve, has reported almost no new cases for more than a month. The news is also promising in Taiwan, Singapore and South Korea.
In ravaged Italy, the number of new cases has flattened over the past 10 days, as has Spain more recently. If – and it's a big if – these trends persist for weeks rather than days and replicate in other countries, we might cautiously dismiss the gloomiest projections of 50 per cent or higher infection rates and millions of deaths.
As Wuhan resumes normal activities we will have a first glimpse of whether the virus is lurking and poised for another run through the population. The U.S. and Brazil have offered to test the efficacy of early-stage denial, erratic leadership and internally conflicting perspectives. India, the world's biggest democracy, is attempting to lock down 1.3 billion people, many of whose poor face daunting public health challenges.
So far Saskatchewan is faring no better and no worse than its sister provinces. The health impact is more like Germany and Australia than Italy and Iran. Canadian governments have been consistent and unified in their messaging. Reports from B.C. suggest that most people are doing what is asked of them and the case numbers are encouraging. It's still the early days, but so far, so good.
Success begins two metres apart.
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