“The graph that really grabbed my attention was the one showing a model of daily new cases of Covid-19 with social-distancing measures starting just one day apart,” Dr. Britta Jewell said. “It only takes a one-day difference in action to see a 40 percent reduction in cases — that’s enormous. It really conveys the urgency of the situation.”

Working in Excel, she composed a graph showing the power of one case averted now, today — versus one case averted a week from now — in an effort to convey to people what she called “the positive side of exponential growth.”

Using the current case counts from the U.S. as of Friday morning, she calculated what the epidemic would look like if cases grew by 30 percent every day for a month — they have been growing by 30 to 40 percent every day for a week — then looked at what would happen if just one of those infections were prevented tomorrow instead of a week from now.