Second, Covid-19 mutates much more slowly than influenza, and its key spike protein — the part of the virus that attaches to cells — seems particularly stable. Amid all of the bad news that this virus has brought, this characteristic of the virus is a silver lining in several ways.

Since the virus does not mutate nearly as fast as influenza, this reduces almost to zero the chance that it will become more virulent, as happened in 1918. Moreover, because the spike protein is a key part of the virus likely to be recognized by the immune system, then mutation will probably not account for a new wave soon. For the same reason, the consensus view of virologists seems to be that those who recover from the illness probably develop immunity lasting a year and possibly longer, and that a vaccine will most likely protect reasonably well against Covid-19.

Third, the incubation period, on average nearly six days, is roughly triple the average incubation period of influenza, and the disease itself takes much longer for people to recover from and stop shedding virus. Therefore even without social distancing it would take months for the outbreak to pass through a community, as opposed to six to 10 weeks for influenza. With social distancing — necessary to reduce deaths by keeping hospitals from being overwhelmed — it will take even longer. Additionally, the incubation period allows an asymptomatic person more opportunity to spread disease.

But these factors will give the country more time to expand testing and contact tracing, and to isolate and quarantine contacts. All of those are impossible with fast-spreading influenza.

How then do we restart the economy? We cannot simply wait for herd immunity to develop from natural infection. That would take many months and be accompanied by an unacceptable death toll. Nor can we wait a year or more for a vaccine.

Instead, a consensus has formed among public health experts to continue current measures until the epidemic curve bends significantly downward and the stress on health care is alleviated, followed by a phased-in approach guarded by, in effect, a public health army. That army would be fighting a guerrilla war, armed with tests, tracing, isolation and quarantine to search and destroy inevitable flare-ups.

This approach has worked around the world. It will work here. Covid-19 would continue to spread, but the cases would be in manageable numbers. We would see not so much distinct waves as continuous, undulating swells, broken by occasional angry whitecaps.