There is a lot of uncertainty right now about how severe and how fatal COVID-19 will be in Canada. Are we over-reacting, or are we slow to respond and doomed to require convoys of funeral trucks?

With a simple estimate, I am convinced that we are neither. We finally have enough domestic case data to make some forward-looking predictions, and it seems that we are still at a critical point — teetering between being able to cope appropriately and having to decide who lives and who dies.

Extrapolating Canada’s COVID-19 cases two weeks into the future. Original image by the author, with statistics from https://www.canada.ca/en/public-health/services/diseases/2019-novel-coronavirus-infection.html. The most up-to-date plot is at the bottom of the article.

The onset of epidemic outbreaks is characterized by exponential growth. Conveniently, this growth can be described with a single important number — the doubling time.

From the Government of Canada’s daily numbers, the doubling time of Canada’s COVID-19 cases is around 2.6 days. Because of the time it takes for new infections to incubate, manifest symptoms and be diagnosed, we need approximately 14 days for our official statistics to reflect any actions we take. In two weeks there will be 5.4 doubling times, so we can expect a whopping 42x increase in cases before we can see how effective our efforts are. This brings us to nearly 20,000 cases by the end of March.

At least 2% of COVID-19 patients (could be up to 5%) need intensive care, and our health care system usually only has 500 available intensive care units (~10% vacancy in 5,000 total units). This means we’ll be at critical capacity somewhere around 25,000 COVID-19 cases. This estimate is coarse, but with a 2.6 day doubling time it is clear that there is not much margin.

Had our federal and provincial policies come into place just two days later, we would be on track for certain disaster in April. Had the policies come in two days earlier, we might have had an easy chance at containment.

This high sensitivity to timing is a property of exponential growth that is only apparent late in the curve.

What matters now (still) is how effective our present-day social distancing actions are. We won’t know until April, but our actions now will dictate whether or not we bump up against our health system’s capacity.

Within capacity

If March really brings us close to 25,000 cases, we will need our actions now to be as effective as China’s lockdown, which almost immediately halted new cases.

If they are, we’ve successfully “flattened the curve” for now. It probably won’t be impressive though: Canada is much less dense than China and we’ve had months to learn from the rest of the world, yet we’re likely to reach 10 times more cases per capita than China.

Above capacity

If we slip, or if it turns out that our efforts are less effective than a complete lockdown, we are likely to reach or exceed the hazy region of capacity.

We have all heard that when hospital beds fill up, things start to look bleak. Our medical staff will be in triage, and people will die needlessly without access to care. Mortality rates could rise to 5% to match those of Iran and Italy.

Each COVID-19 carrier infects on average 2.3 others. Considering 4 downstream transmissions, this means that…

…if you get infected with COVID-19 when the medical system is at capacity, there is a 75% chance that you will be responsible for someone’s death.

Have you ever wanted to save a life? This is your chance to do it with Netflix and Lysol wipes. Don’t be South Korea’s Patient 31.

What now

What does it take to stay within capacity? We’re not sure yet, but we do know that China reduced their new cases to nearly zero immediately after lockdown. Our policies aren’t quite as drastic, so they might not be as effective. On the other hand, maybe the luxury of early testing and a bit of warning will curb our doubling time faster.

We’re all in this together, and by today’s numbers we still have a chance at containing the virus to <0.1% of Canada’s population without overflowing hospitals.

Thank you all for jumping on board, and keep up the timely efforts. We have no more days to spare — certainly not 2.6.