On March 8, it was mostly business as usual in the United States. As the Lakers faced the Clippers in a much-anticipated Los Angeles basketball matchup, Sen. Bernie Sanders (I-Vt.) rallied before a packed crowd in Michigan. In Miami, thousands squeezed onto the beach for a massive dance party. With 500 coronavirus infections reported nationwide at the time, the outbreak seemed like a distant threat to many Americans.

But by the following Sunday, the nation had entered a different universe: 2,000 confirmed cases, dozens of deaths, and shutdown orders in Illinois, Ohio and New York City, among other parts of the country.

What if those sweeping measures imposed by March 15 — a federal warning against large gatherings, health screenings at airports, states of emergency declared by governors and mayors — had been announced a week earlier?

New research from Columbia University epidemiologists offered one possible answer on Wednesday. If the same kind of social distancing had been in place seven days earlier, their study found, the United States could have prevented 36,000 deaths through early May — about 40 percent of fatalities reported to date.

“If you don’t take steps to fight the growth rate aggressively, you get much worse consequences,” Jeffrey Shaman, an environmental health sciences professor who led the study, told The Washington Post.

His team’s analysis used infectious-disease modeling to examine the spread of the virus from March 15, when many people nationwide began staying home, until May 3. The researchers examined transmissions within each county, movement between counties and deaths to chart how the virus spread — and killed — over seven weeks.

Then, Shaman and other researchers modeled another scenario: What if government officials had closed everything down one week earlier?

Unlike some of the forecasts that have made headlines in recent weeks, their model does not attempt to predict how certain policies — say, another month of shutdowns, or partial reopening measures — might affect the virus’s spread. It simply shifts the timeline for the country’s response.

Move it back even further, and the results are more dramatic. If the United States had mustered the same kind of political and public will against the virus on March 1, the researchers found, 54,000 fewer Americans would have died of the illness. By Friday, the nationwide death toll had surpassed 93,000.

The Trump administration blasted the study’s findings following a New York Times report late Wednesday. In a statement to The Post, White House spokesman Judd Deere said federal officials made the best decisions possible with the information available at the time.

“What would have saved lives is if China had been transparent and the World Health Organization had fulfilled its mission,” Deere said. “What did save American lives is the bold leadership of President Trump.”

The president imposed “early travel restrictions when we had no idea the true level of asymptotic spread,” and he organized “the greatest mobilization of the private sector since World War II to deliver critical supplies” and expand testing, the spokesman said.

Trump banned travel from Europe on March 13 and told the nation to “take it easy” and “relax” two days later. It was not until the end of the month that he first used the Defense Production Act to compel factories to produce ventilators.

Shaman said the effectiveness of the country’s virus response relies on decisions made at all levels, from the Oval Office down to individual households. In Cook County, Ill., which includes Chicago, he said, orders from state and local officials as well as compliance from residents seem to have pushed the rate of infection into a decline.

“You could sit there and point the finger at whoever you wanted to,” Shaman said. “In truth, each of us is going to draw his or her own conclusions about where blame may be assigned.”

It is more productive, he said, to take the study’s lessons and apply them to the future, particularly as large swaths of the country move to partly reopen ahead of Memorial Day weekend.

With businesses up and running and Americans leaving their houses more regularly, the country must remain vigilant and swing into action quickly when new outbreaks flare up, Shaman added, pointing to the aggressive steps taken by nations such as South Korea and New Zealand. That requires strong calls to action, too.

“What we have before us is a very, very challenging problem,” he said. “It requires political leadership and public compliance and a will on the part of everybody in society to make it happen.”