As the U.S. and Europe hit the peak of the Coronavirus Pandemic infections and deaths, these countries have begun the debate on unlocking the lockdowns and quarantines.
Let’s look at this graphically to estimate whether this discussions are premature or not. Here’s today’s view of infections, courtesy of The Financial Times and John Burn-Murdoch (with the US curve highlighted by me).
Infections are sigmoid curves, not exponentials. If we take a simple assumption that the infection will slow down as fast as it sped up, then we can just make a copy of the above line, mirror it, and see where it falls.
It took 40 days for the number of cases to grow from 30 to the peak, and thus it takes 80 days in this simple estimate to get back down to 30 cases. 80 days being another 40 days of lockdown. Today is April 18, so that would be May 28.
However, if you look at the countries that are “over the hill” of the curve and headed back down to 30 cases, the slope on the down side of the curve is not as steep as the growth of infections on the up slope.
New Zealand is one country that is on its way to eradicating its outbreak, and it did that without the authoritarian practices seen in China nor the massive testing and efficiency of South Korea, neither of which are likely to ever be matched by the United States. If we take the second half of the New Zealand curve, scale it up to the United States and tack it onto Day 40, we get the following.
The results don’t fit on the graph. At Day 90 there are still 1,000 new cases per day. That would be great, as we’re currently experiencing over 30,000 cases per day, but the lockdowns started when we first hit that rate. Unlocking at 1,000 cases per day very likely puts us back at 30,000 cases per day 30 days later.
Instead, let’s extend the graph and see what is probably close to reality. Given what we’ve seen in New Zealand, Australia, Norway, Austria, and South Korea, this simple projections shows it’ll be after Day 100 when the number of new cases in the United States is down below 100 per day. Down in the range that China and South Korea are experiencing today. Down in the range where they are proving it possible to undo the lockdowns without a resurgence of exponential growth.
Day 100 is 60 days from today. June 17, 2020.
The talk of restarting life on May 1 is simply too soon. So will be June 1. If the current trends continue, maybe the middle of June will be safe. My suggestion is that we plan on July 4th, celebrating an extra special Independence Day, complete with fireworks, but without the parades and crowds.