Michael S. Saag is associate dean for global health and the director of the Center for AIDS Research at the University of Alabama at Birmingham.

In Steven Spielberg’s 1975 film “Jaws,” a great white shark haunts the beach community of Amity Island. Police Chief Brody declares the beaches off-limits but is overruled by the mayor. Fourth of July is approaching, and all the island businesses depend on a successful holiday weekend. After an innocent tiger shark is captured, the mayor declares the problem solved. As vacationers swarm into the water, the real predator shark kills a young boy paddling on a raft, and a second round of panic floods the island.

Today our country is being attacked by a predator virus. By the end of April, it almost certainly will have infected more than 1 million people here, resulting in up to 60,000 deaths. Since early March, most states have announced “stay at home” restrictions that are successfully flattening the curve of anticipated cases. Though many hospitals have been stretched to capacity, those orders averted a catastrophic implosion of health-care systems and saved lives.

But stay-at-home policies were implemented at a high cost. The closing of small businesses, restaurants, bars and other “non-essential” activities resulted in a huge spike in unemployment, economic hardship for tens of millions of citizens, and near-collapse of the economy. Pressure is building for release of the restrictions and a gradual return toward normalcy.

Ending restrictions without plans based on sound public health principles, however, will almost surely result in a new wave of cases, putting us right back where we were in early March. The virus is lurking just under the surface of our frustration. The vast majority of Americans remain susceptible. It doesn’t matter if the restrictions are lifted on May 1, June 1 or July 1 — without reentry plans grounded in science, we’re headed for Amity Island outcomes.

Most of the current state proposals for reopening society rely on social distancing, screening workers for symptoms of covid-19, asking those who feel ill to refrain from coming to work and frequent hand-washing. These are nice steps. But since up to 50 percent of transmissions of the virus occur before symptoms develop, with the peak time of transmission beginning in the five to eight hours before the onset of symptoms, these safeguards are not enough.

The proposed interventions alone will almost certainly fail and result in a new surge of cases. It will take 14 to 28 days for the spike to be noticed, and probably another week or two for a second stay-at-home order to be issued. By that time, the health-care systems will be once again swamped, fatigued health-care workers will be called on to again perform heroic feats, and the cry will go up, “Will this ever end?”

There’s a better way to reopen society — and it’s no secret: It’s testing.

Public health officials use this approach every day in controlling infectious diseases such as tuberculosis. It employs aggressive, early testing of those with symptoms (index cases), along with isolation and testing of all those who had close contact with the index case until their status is determined. Other countries, including South Korea, Israel and Germany, are accomplishing contact tracing with the aid of an expanded workforce and information technology. The index cases are treated and placed in quarantine. This process minimizes exposure and can allow us to gradually lift restrictions and begin safely returning toward normalcy.

The final piece of the public health approach involves widespread random testing to identify who has had prior infection and thus might have immunity (a condition yet to be proved, but which seems likely).

The United States has expanded covid-19 testing capacity significantly in recent weeks, with up to 4 million tests being administered, currently around 140,000 a day. Unfortunately, estimates summarized by the Kaiser Family Foundation indicate that between 500,000 and 4 million tests daily will be required to manage the U.S. pandemic. The tests alone will cost billions per month — and there will also be the cost of personnel and staffing needed to manage them. No state can afford its share of this; the federal government must act.

In “Jaws,” the rush of Amity Island’s mayor to declare the beaches safe to save the economy without addressing the real problem — a predatory shark — led to needless deaths. Rushing forward to drop stay-at-home policies without first tackling the greatest need — testing — will have the same outcome.

It’s going to take a bit more time and significantly more money. It’s a national need requiring a national solution. States can help with stay-at-home orders, but the federal government needs to deliver on testing.

To paraphrase what Chief Brody said when he first saw the actual size of the shark: We’re going to need a bigger boat.

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