The 1918 influenza outbreak infected roughly one-third of the world’s population at the time, yet — on the surface — it didn’t seem to leave its mark on art and literature the way World War I did. But scholar Elizabeth Outka, author of “Viral Modernism: The Influenza Pandemic and Interwar Literature,” argues the pandemic’s influence is an undercurrent that runs through many works of the period. Host Marco Werman speaks with Outka.