It can’t go on like this, can it?

As the coronavirus lockdown drags on and the economic pain deepens, more and more people are asking that question. And as they cast around for an alternative, they’re asking another question, posed by Fox News host Tucker Carlson on Thursday night: Why do we all have to shut ourselves inside? Can’t we just isolate the old and the vulnerable, while the rest of the country goes about its business?

When you first hear it, this seems like the blindingly obvious answer to all our problems. Unfortunately, once you examine the mechanics of putting this concept into action, it turns out to be very obviously a bad idea.

For one thing, younger people get sick, too — often very sick. Based on early data from China, health authorities initially emphasized that most of the deaths are occurring among the elderly, which unfortunately created an enduring impression that this is just a strange sort of influenza that happens to kill huge numbers of old people.

In fact, it’s much worse than flu for every age group except young children. Young adults are being hospitalized, and even put on ventilators, at a disturbingly brisk clip. Middle-aged people face a risk of dying that is lower than among the elderly, but still substantial: So far, among known infections of Americans aged 45 to 54, 5 percent to 10 percent ended up in intensive-care units, and at least 0.5 percent died. That translates into a 1-in-200 chance of dying for those infected. Even assuming that hospitals could handle the caseload, and there are a good number of asymptomatic cases we aren’t measuring, that risk is unacceptably high.

Under the Carlson plan, a lot of people would face those risks. As you’ve probably read elsewhere, one of the main reasons that the novel coronavirus is so deadly is that it’s novel. No one’s had it; no one has antibodies to it. So it can burn through the population rapidly, because it never dead-ends at people who are already immune. Especially because it takes so long for the infected to show symptoms.

“It’s insidious in onset,” a doctor who has had covid-19 told me. “With flu, you wake up one day and are like ‘I feel like death.’ ” With covid-19, all she had for several days was a little sniffle and a loss of her sense of smell; the really nasty symptoms didn’t show up until the fifth or sixth day.

That’s fairly typical of coronavirus patients; the virus gives them days to walk around, shedding infection upon everyone they come into close contact with. Given how contagious this disease is, and how severe the symptoms often become, if we tried a “quarantine the vulnerable” plan, it’s very likely that many hospitals would be overwhelmed even if they didn’t have any older patients.

Moreover, it’s not even possible to quarantine the vulnerable. Some 24 percent of adults between the ages of 55 and 64, and 21 percent of those over age 65, live in a multigenerational household. So, of course, do millions of younger immunocompromised or otherwise medically vulnerable adults and children.

If the rest of the populace is merrily going about its business, infecting each other with abandon, those people will inevitably get exposed unless the vulnerable ones can move to a separate household, or the other people in the household also self-quarantine indefinitely. Because people often live with relatives precisely because they can’t afford to live separately — much less off their savings — this is not very practical.

Okay, so why not provide them temporary separate housing? Well, unless you’ve got a way to instantly throw up millions upon millions of nice apartments, you’re talking about putting them in some kind of barracks. This will have to be serviced by younger people brought in from the outside world, who will eventually bring covid-19 in with them. At which point, you will discover that instead of protecting the elderly and vulnerable, you’ve gathered them all into one place, where the virus can mow them down more efficiently.

This problem will also affect the places that are already housing the elderly: nursing homes, assisted living facilities and senior communities. Plus millions of homes where elderly people are living independently with the assistance of visiting family or health-care workers. Furthermore, the residents of those places not infrequently have heart attacks or strokes or hip fractures, necessitating trips to hospitals that would be overrun with younger covid-19 patients.

“Just isolate the vulnerable” is one of those solutions that sounds incredibly plausible, even obvious, until you get into the details. But as soon as you try to figure out exactly how it would work, you quickly see that it is actually a remarkably efficient way to kill an unthinkable number of people, which is why Britain, which had initially considered using essentially this strategy, soon abandoned the idea, and moved to the same strategy as the rest of the world: try to reduce transmission until the disease can be controlled by testing and spot-quarantines, rather than national lockdowns. There is no easy way out of this, no simple solution that somehow eluded the experts. There is only a miserable tradeoff between economic production and human lives.

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