If you’re over 75, catching covid-19 can be like playing Russian roulette

Are you hiding from covid-19? I am. The reason is simple: the high chance of death from the virus.

I was reminded of the risk last week by this report from the New York City health department and Columbia University which estimated that on average, between March and May, the chance of dying if you get infected by SARS-CoV-2 was 1.45%.

That's higher than your lifetime chance of getting killed in a car wreck. That's every driver cutting you off, every corner taken too fast, every time you nearly dozed off on the highway, all crammed into one. That's not a disease I want to get. For someone my mother's age, the chance of death came to 13.83% but ranged as high as 17%. That's roughly 1 in 6, or the chance you'll lose at Russian roulette. That's not a game I want my mother to play.

The rate at which people are dying from the coronavirus has been estimated many times and is calculated in different ways. For example, if you become an official covid-19 case" on the government's books, your death chance is more like 5%, because you're sick enough to have sought out help and to have been tested.

But this study instead calculated the infection fatality ratio," or IFR. That's the chance you die if infected at all. This is the real risk to keep in view. It includes people who are asymptomatic, get only a sniffle, or tough it out at home and never get tested.

Because we don't know who those people who never got tested are, IFR figures are always an estimate, and the 1.45% figure calculated for New York is higher than most others, many of which fluctuate around 1%. That could be due to higher rates of diabetes and heart disease in the city, or to estimates used in the study.

It's also true that your personal odds of dying from covid-19 will differ from the average. Location matters-cruise ship or city-and so do your sex, your age, and whether you have preexisting health conditions. If you're in college, your death odds are probably lower by a factor of a hundred, though if you're morbidly obese, they go back up. Poor health-cancer, clogged arteries-also steeply increase what scientists call the odds ratio" of dying.

The biggest factor, though, is age. I looked at the actuarial tables, and the chance of death for a man in my age group (I'm 51) is around 0.4% per year from all causes. So if I get covid-19, my death chance is probably three times my annual all-cause annual risk (since I am a man, my covid-19 risk is higher than the average). Is that a chance I can live with? Maybe, but the problem is that I have to take that extra risk right now, all up front, not spread out over time where I can't see or worry about it.

Tbh, these % don't help me. More useful would be a list of comparable risks associated with common behaviours that I uncritically accept. Do you know of any examples?

- Andrew Harmer (@andrew_harmer) July 1, 2020

On Twitter, some readers complained that average risks don't tell them much about how to think or act. They have a point. What's a real-life risk that's similar to a 1.45% chance of dying? It wasn't easy to think of one, since mathematically, you can't encounter such a big risk very often. Skydiving, maybe? According to the US Parachute Association, there's just one fatality for every 220,301 jumps. It would take 3,200 jumps to equal the average risk of death from covid.

Risk perceptions differ, but it's the immense difference in IFR risk for the young (under 25) and the elderly (over 75) that really should complicate the reopening discussion. Judging from the New York data, Grandpa's death chances from infection are 1,000 times that of Junior. So yes, we need schools to keep kids occupied, learning, and healthy. And for them, thank goodness, the chances of death are very low. But reopening schools and colleges has the ugly side effect that those with the lowest risk could be, in effect, putting a gun to the head of those with the highest (although there is still much we do not know about how transmissible the virus is among children).

The virus is now spreading fast again in the US, after the country failed to settle on a strong mitigation plan. At the current rate of spread-40,000 confirmed cases a day (and maybe five to 10 times that in reality)-it's only two years until most people in the US have been infected. It means we're pointed toward what, since the outset, has been seen as the worst-case scenario: a couple of hundred million infected and a quarter-million deaths.

By now you might be wondering what your own death risk is. Online, you can find apps that will calculate it, like one at covid19survivalcalculator.com, which employs odds ratios from the World Health Organization. I gave it my age, gender, body mass index, and underlying conditions and learned that my overall death risk was a bit higher than the average. But the site also wanted to account for my chance of getting infected in the first place. After I told it I was social distancing and mostly wearing a mask, and my rural zip code, the gadget thought I had only a 5% of getting infected.

I clicked, the page paused, and the final answer appeared: Survival Probability: 99.975%".

Those are odds I can live with. And that's why I am not leaving the house.