Universities, nursing homes, and even entire cities are turning to an unlikely tool to monitor the spread of the coronavirus: sewage water.  CNN Chief Medical Correspondent Dr. Sanjay Gupta talks to infectious disease physician Dr. Amy Mathers about how sewage testing is playing out on the campus of the University of Virginia, and how researchers around the country could use the testing to detect the virus early.To learn more about how CNN protects listener privacy, visit cnn.com/privacy