Disease modelers at Columbia University estimate that if the United States had started implementing social distancing and lockdown measures one week earlier in March, roughly 36,000 coronavirus deaths could have been prevented.

The first imported case of COVID-19 in the United States was reported on Jan. 20, with community transmission established in the weeks following. Federal social distancing measures, which asked Americans to avoid unnecessary travel and social gatherings, were enacted in the U.S. in mid-March. The researchers estimated that had action been taken even earlier, with cities going on lockdown and people limiting contact with others beginning on March 1, about 83 percent of the country’s deaths could have been avoided.

Epidemiologist Jeffrey Shaman, who led the research team, told The New York Times that just a slight change in timing would have stopped the worst exponential growth in cities like New York and New Orleans. “It’s a big, big difference,” he said. “That small moment in time, catching it in that growth phase, is incredibly critical in reducing the number of deaths.”

The modeling shows that as restrictions continue to relax across the United States, local officials need to know how many infections there are in order to immediately address any hot spots. As of Wednesday night, there are more than 1.5 million confirmed coronavirus cases in the U.S. and 93,383 deaths.