Schools and vulnerable populations present more intractable problems. On the one hand, schools might seem easier to open than many other venues, because children are less vulnerable than adults to death or serious illness from the virus. Moreover, we still don’t know the degree to which children — who rarely manifest symptoms — can even spread the virus. Keeping schools closed for an extended period will do enormous long-term harm to the future of this generation of children, and in the short term we’ll also be trapping many parents at home, out of the workforce — and parents are surely desperate to get their kids out of the house and back in school anyway. But parents are also extremely risk-averse when it comes to threats to their kids’ health, and children can still occasionally become gravely ill as a consequence of the virus. Reopening the schools without the kind of rigorous testing regime being experimented with in Europe will likely mean that those socially and financially able to keep their kids home will continue do so, while most parents will have no choice but to take the risk.

Protecting the most-vulnerable is similarly intractable. Nursing homes are places where elderly and infirm are already isolated, and they have generally done a poor job of keeping infection out. But elderly relatives being cared for in multigenerational households are also highly vulnerable to infection from other household members — a big factor in the high death toll in Italy. And a huge number of non-elderly Americans are rendered more vulnerable to the virus’ depredations by underlying conditions like diabetes, heart disease and obesity. It’s impossible to imagine that they could all be adequately protected under even semi-normal conditions. Nonetheless, a plan for failure means a plan for managing this higher risk: supporting programs, such as a vastly expanded corps of visiting nurses and other aides, to make it more practical for individuals who need to be isolated to achieve that isolation.