The next round of social distancing will be activated more rapidly, because officials — and the public — will be more prepared. It should also be shorter, because we can assume that most of the people who were initially infected are likely to be immune next time around. But it will still disrupt people’s lives and the economy. We will still have canceled conferences and sporting events. People will not frequent restaurants and will not travel. The service industry will be severely curtailed. And it’s going to happen again and again.

Maybe the best analogy is pumping a car’s brakes on an icy road. Either doing nothing or slamming on the brakes leads to an accident. So we pump the brakes — pushing on the brakes, then easing up, and then applying them again — and after three or four times we slow down enough to stop.

When will the coronavirus be tamed like influenza, if not conquered like smallpox? A vaccine would need to be administered to an estimated 45 percent to 70 percent of the population — at least 145 million people — to stop the spread of the virus. If we are lucky, and an effective vaccine is quickly developed, this could happen by the fall of 2021.

It might even be sooner if researchers can come up with an effective treatment that, in addition to preventing deaths, reduces the infectiousness of each case. One antiviral drug, remdesivir, has shown promise in treating monkeys infected with a similar coronavirus, and is being studied in humans. Trials of other drugs will begin soon. Again, if we are lucky, these trials may identify one or more effective treatments in four to five months.

The alternative to this roller coaster would be even more drastic. It would require sustaining social distancing until there are no more cases whatsoever and then closing borders to all travelers — no contact with the outside world — for 18 months or more. While the United States and many other countries, like Denmark and Germany, have instituted travel bans, sealing the country off for over a year until a coronavirus vaccine is discovered seems implausible. But who knows. If the situation becomes dire enough, the previously impossible could become inevitable.

On a positive note, each time the virus resurges after social distancing is relaxed, it will do so more slowly. But the flattened curve we are all hoping for — the one that is so critical to our health care infrastructure — will not actually be flat. It is more likely to be a series of ascents and descents, with dampened oscillations. So all of us — health care workers, policymakers and American citizens — need to get ready for a bumpy ride.

Ezekiel J. Emanuel is the chairman of the department of medical ethics and health policy at the University of Pennsylvania, where Susan Ellenberg is a professor of biostatistics and Michael Levy is a professor of epidemiology.

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