While many institutions across the country were modeling the trajectory of COVID-19 at the national level, Dr. David Rubin, and his colleagues at CHOP’s PolicyLab took a more innovative approach: They mapped the spread of the virus at the county level. More than 500 U.S. counties are included in the PolicyLab model, which has been used by local and state policymakers, as well as the White House Coronavirus Task Force. Dr. Rubin discusses how the model came to fruition and shares the most surprising – and important – thing researchers have learned from it.