As you might imagine, this is basically an impossible question to answer, but it’s important to try anyway. There are a lot of variables that go into any attempt at coming up with a realistic estimate, so from the outset, let me explain a few things about the numbers you’ll see below. First, I came up with the range of death rates (corresponding to possible rates of asymptomatic infections) by trying to figure out a more appropriate comparison between the flu and the new SARS-CoV-2 virus. A lot of people have been making some very bad, completely logically invalid comparisons between the direct observations being recorded for COVID-19 and the statistically derived annual numbers for the flu. In order to get a more appropriate comparison, we’d need a valid statistical analysis of COVID-19, something we don’t have enough time or data under our belts yet to completely understand.
But, being the curious person I am, I took my best guess. (My analysis, just like everyone else’s the world over, will continue to evolve over the months and years ahead, as we all learn more. But for now, this is the best I can come up with.)
For a refresher, here’s the data I derived using an asymptomatic range from 33% to 75% for the flu:
And here’s the data I derived using a similar asymptomatic range from 33% to 75% for COVID-19:
Basically, during a typical flu season, between 12% and 35% of Americans catch the flu, and about 37,000 people die from it. Through June 1, when I did my calculations, between 1% and 5% of Americans had caught the coronavirus, and more than 100,000 people had already died of it. (Of course, we don’t know for certain the asymptomatic rate of infection for either virus, but the studies and reports lead me to believe that these are acceptable ranges to use to make my guess.)
The numbers for SARS-CoV-2 are not good, to say the least. Sure, they could be worse: Maybe we’re not looking at a new Black Death, but we’re definitely staring down a new Spanish Flu. Exactly how bad it will be is going to rely on a few factors.
How Many People Need to Get Sick?
To beat this virus, or at least slow it and manage it, we need one of two things: a vaccine or herd immunity. Let’s assume that a vaccine is years away, if it’s even possible. (Remember, we’ve never created a vaccine for a coronavirus. Also, the shortest time span in which we’ve created and deployed a vaccine in the past was five years—for the measles, when the first test for the vaccine in 1958 proceeded until the vaccine itself was licensed and distributed in 1963.)
So, in the shorter term of the next couple of years, herd immunity is our best bet to wipe out the disease. According to Johns Hopkins: “Depending how contagious an infection is, usually 70% to 90% of a population needs immunity to achieve herd immunity.” With a national population of about 330 million people, that’s between 231 million and 297 million Americans who are going to get infected before the spread stops in this country. (It will probably slow before that, but won’t stop until we actually reach herd immunity.)
How Quickly Will We Let It Spread?
The virulent nature of the disease matters. A virus that spreads more difficultly and slowly, like the original SARS or Ebola, can be contained more easily. You can also slowly creep up on the lower threshold of 70% and have it be effective.
A more virulent disease is going to blow past that 70% lower threshold while it’s still spreading. These more virulent diseases—like the flu, measles, or even the common cold—spread more fluidly through populations, and outbreaks can get out of control more quickly.
By all accounts, SARS-CoV-2 is the latter. There continues to be some debate over how many have already caught it and how many cases are asymptomatic and mildly symptomatic—and whether those infected people still spread the virus (and, if so, how easily)—but by all accounts this virus spreads easily and fluidly with little in the way of natural barriers to slow it down. For months, we have shut down half of our economy and most of us have sheltered in our homes as much as possible—two things we have never done for any disease … in the history of our country—and yet this thing is still spreading like crazy with cases and hospitalizations yet again on the uptick.
This new increase in cases doesn’t even qualify as a second wave, since we never really brought down our caseload from this spring enough to consider the first wave over. Can you image how bad this would have become by now if we had conducted business as usual since March? It’s a terrifying thought.
So while getting to herd immunity might technically only need 70% of the population, in order to hit that low end of the range would require a very slow spread and a gradual infection rate. That’s unlikely to happen. At this point, hitting that 90% infection rate for herd immunity to truly kick in is far more likely.
So What Does All This Mean?
Basically, between 70% and 90% of Americans—between 231 million and 297 million people—might have to catch the coronavirus before we can slow and stop this disease. With a range of death rates between 0.58% (if the virus has a 75% asymptomatic rate) to 1.56% (if the virus has a 33% asymptomatic rate), we’re probably looking at a level of devastation in the ranges below:
70% Herd Immunity Level
33% Asymptomatic (1.56% death rate): 3.6 million people
50% Asymptomatic (1.17% death rate): 2.7 million people
75% Asymptomatic (0.58% death rate): 1.3 million people
90% Herd Immunity Level
33% Asymptomatic (1.56% death rate): 4.6 million people
50% Asymptomatic (1.17% death rate): 3.5 million people
75% Asymptomatic (0.58% death rate): 1.7 million people
So our best-case scenario (at the low-end 70% infection rate with 75% being asymptomatic) is 1.3 million Americans dead. In the worst case (at the high-end 90% infection rate with 33% being asymptomatic) is 4.6 million Americans dead.
On June 29, as I write this, 125,000 Americans are dead from this horrible disease. So what my estimates above show is that we are just getting started.