Archive for March, 2020

COVID-19 and God’s List: assessing personal risk from the novel coronavirus

How dangerous is the novel coronavirus, and how does that risk compare with other risks we face in our lives? A bit of number sense and a few simple calculations allow us to visualize, and hence compare, the risks.

Imagine God has a book with the names of all people living in America today. Against each name, he has entered the cause of their death. (He’s God, so he has the death entries now.) He won’t let you see your entry. You do, however, have a chance to look at the book. Not close enough to read the individual entries, but close enough to discern the separate entries as such. You ask him to re-order the list grouped by the listed causes of death. (It’s a digital book.)

The biggest group is labeled “heart disease”. Roughly 1 in 6 of the names on the list are in that group. As a decimal, approximately 0.167. [That’s a figure quoted regularly in the medical profession. For example, this article. The exact values are not important to get an overall picture of the risks.]

This year, God had to add a new category: COVID-19. Right now, you are worried about it. You should be, and should do everything you can to avoid it. But in the overall scheme of things, how big a risk is it? Let’s run a few numbers.

Well, let’s suppose the infection reaches 60% of the population. That is the point where the growth ceases to be exponential (because there are not enough non-immune hosts left to fuel such rapid growth). The penetration could go higher, but at a much slower rate, which means medical services are not overwhelmed and more sick people can be saved.

The best current estimate we have for the mortality rate is 1%. (Congressional testimony of Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases.)

So, in a population of 327M, the proportion who will be infected and subsequently die is 327 x 0.6 x 0.01M, which works out to 1.96M. As a proportion of the entire population, that is 0.006.  Six in every thousand, or 0.6%. Putting it another way, 994 of every 1,000 people in the United States today will survive.

That sounds encouraging, and it is, but it’s a lot higher than the risks associated with most of the actions we take in daily life, such as getting on a plane, driving across town, or crossing the road. Moreover, in particularly severe cases, the illness can be very unpleasant, even if you survive. All in all, it’s definitely something you should try to avoid.

But how does the risk of COVID-19 death stack up against the other things you may die of? More specifically, where does COVID-19 come on God’s List? The answer is, pretty low down the (reordered) list. The group of names that have that label in the “cause of death” column is (roughly) just 1/28th the size of the heart disease group.  [.006/.167 = 1/28 approx.]

But be cautious. COVID-19 presents a different kind of risk than heart disease. The latter is something that creeps up over your lifetime, and, if you get medically examined regularly and you are found to have it, you usually have plenty of time to modify your activities and habits to slow it down or even stop it developing further.

With COVID-19, however, it is a risk that (we all hope) you will only face in 2020 (because by 2021 we hope to have an effective vaccine), and the length of time you have to change your behavior to save yourself is measured in a few weeks (if you are following the news from a reliable source), or maybe just days. On the other hand, the behavioral changes required are very simple, albeit involving a major disruption of your daily life. Thoroughly wash your hands regularly, apply hand-sanitizer after coming into contact with any person, pet, or object, avoid touching your face, and keep at least six feet from any other person.

Nevertheless, in terms of what God has entered against your name as the cause of your death, it’s highly unlikely to be COVID-19. It’s 28 times more likely to be “Heart failure”.

In other words, what the numbers tell us is that you are extremely unlikely to die from COVID-19, whatever you do. But, assuming you’d rather live than die (and would rather avoid a terrible illness even if you survive it), then if there were actions you could take to make your odds for not dying from this virus, you should take them.

As we just saw, the actions required are a nuisance, but you only have to do them until the virus simply goes away (not likely) or we find an effective vaccine (highly likely within a year, maybe a bit more). So COVID-19 presents a numerically small danger made acute by being entirely within a single year or a year-and-a-half. Avoidance is simple, and is required for a relatively short time, but it’s a nuisance.

In the case of heart disease, the same conclusions follow, but the time-scale is very different. In this case, it’s one of a small collection of illnesses (around ten) that you are highly likely to die from, but the threat lasts your entire life. Avoidance measures are also simple (principally diet, exercise, and not smoking), but need to be sustained.

The take-home message, then, is that during this year (and maybe into next), COVID-19 is a threat you should not treat lightly. But in terms of God’s List, this is most unlikely to be what he has entered against your name. (“Heart disease” is far more likely.)

So, given how heavily the overall odds are stacked in your favor, the incentive to take COVID-19 avoidance measures is huge, since they are almost certain to be effective. Besides, with a virus epidemic, avoidance measures any one of us takes benefit all of society, including our families, friends, and loved ones.

If you do come through the COVID-19 epidemic, then, on January 1, 2021, with the novel coronavirus threat behind you (or at least soon to be so), you will be in a position to make a New Year Resolution to make sure your diet and exercise habits can fend off heart disease. That’s a deadly threat that continues throughout your life. And the odds that this killer is the one that gets you are a lot higher than for that virus you just dealt with. Why get through one threat and then squander your chances to avoid a much greater one?

NOTE: This article has a good description of the various ways COVID-19 can spread and how we can prevent them.


I’m Dr. Keith Devlin, an emeritus mathematician at Stanford University, an author, and was for many years “the Math Guy” on NPR’s Weekend Edition. Off duty, I’m an avid cyclist. (The header photo is me halfway up Mt. Baldy in Southern California.)

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