“Social distancing bends the curve and relieves some pressure on our heroic medical professionals. But in order to shift off current policies, the key will be a robust system of testing and monitoring — something we have yet to put in place nationwide,” Obama wrote in a tweet Wednesday morning.

Guidelines from the US Centers for Disease Control and Prevention note that “decisions about testing are at the discretion of state and local health departments and/or individual clinicians,” and Trump has not floated the idea of a national system for testing and monitoring people stricken with the virus, like China and South Korea are doing.