“One of the biggest challenges with COVID is the number of people who are asymptomatic carriers,” Danielle Allen, lead author of Monday’s Resilience report and a professor at the Edmond J. Safra Center on Ethics of Harvard University, told ABC News. “It’s hard to zero in on the number, but 20% to 40% of people who have the virus are asymptomatic. … That means you’ve got a whole lot of people out there spreading the virus around, and we haven’t been able to do anything about it.”