Flu pandemics recur reliably but unpredictably every decade or so, and their extent and intensity varies. With COVID19, we may be in midst of a once-every-50-years event, perhaps similar to 1957 pandemic, but not as bad as the 1918 pandemic. Let’s talk about the 1957 pandemic. 1/

— Nicholas A. Christakis (@NAChristakis) March 14, 2020