Many key variables change the outcomes significantly. I've heard epidemiologists talk about reducing the "populations" down to things like schools. But then they assume "everyone interacts with everyone". Hence they predict very high infection rates. Michael Levitt takes into account our typically small social circles and predicted Chinese "end" accurately (2-3%). The message is of course, physical distancing works and with our personal circles rather small, it works quickly. I am looking for Levitt's published algo but no sign, I'm going by reports. He is a Stanford Prof so likely legit.