Vespignani told the Yahoo News “Skullduggery” podcast that his modeling is much higher than official estimates because of what he has described as “invisible chains of transmission” of the virus throughout the United States in January and February — before top Trump administration officials grasped the severity of the crisis. By tracking travel numbers and other data, Vespignani said he and his associates have been able to trace the course of potential spreaders who had returned to the country from China and other nations where the virus had spread.

He said the aggressive social distancing measures most Americans have undertaken doubtless saved several hundred thousand lives. New cases of COVID-19, the disease that results from exposure to the coronavirus, have plateaued as a result, Vespignani said. But he warned that reopening public spaces too soon or without adequate testing and contact tracing infrastructure in place could lead to a dramatic resurgence in infections and deaths.