Humans are woefully terrible at understanding the impact of exponential growth. Here’s an example.
An article in the NY Times looked at CDC data for COVID-19 and found something interesting: “By the time 50 cases were officially confirmed, at least 1,200 people had already started showing symptoms of COVID-19, the disease caused by the virus.”
If you do the math, this means that there were 1200 / 50 = 24 times as many people infected compared to the number of confirmed cases. As I’m writing this Thursday evening, there are 245,080 Coronavirus cases known, which means that there might be 5.9 million people actually infected right now.
Take that number with a huge grain of salt (or a barrel of regular sized grains of salt). Because the growth rate isn’t constant, and external factors — like how well we are behaving at social distancing and washing our hands — can reduce growth considerably.
And who knows, maybe someday we will even have enough test kits and doctors so that when Donald Trump says anyone who wants to get tested, can be tested, he won’t be a pathological, pants-on-fire, lying asshole. That would help, too.
However, there are other potential external factors — like hospitals becoming overwhelmed, people running out of food or losing their jobs or homes — that could make the growth worse. Much worse.
But let’s say that the growth stays the same (even though it won’t). What is the interval of time that it takes between the time that someone gets infected and when they are a confirmed case? This includes how long it takes after someone is infected before symptoms appear (estimated to be 5 to 14 days), how long it takes before they can take the test (highly variable), and how long to get the results back (around 4 to 8 days now, but will get longer if hospitals get overloaded).
We don’t actually need to know precisely how long it takes. Whether it takes a week or a month (much more likely to be somewhere between that) the result of exponential growth is the same, it just takes longer.
In that amount of time, the number of people who are likely to be currently infected right now (roughly 5.6 million people) will grow around 24 times and turn into 141 million people. It just doesn’t matter if that takes a week or a month.
The only solution is to stop the rate from growing at all, by any means at our disposal. The magic number is to make it so that on average each infected person infects less than one other person. We know how to do it, now it is up to us to just do it.
(While I was writing this, the number of cases rose again, and the number deaths also increased a bit.)