In fall 2020, due to the Covid-19 pandemic and the looming flu season, public health experts feared the possibility of a “twindemic”—a one-two punch of Coronavirus plus influenza. But that year, flu cases hit historic lows. The so-called twindemic never happened. Milliman health care expert Ellyn Russo discusses why the volume of flu cases decreased, and what health care systems can learn from this phenomenon.