THE BAFFLING SPREAD OF the novel coronavirus has given many scientists and policymakers pause. There may be some important clues in the patterns the disease is leaving that tell us quite a bit about what conditions can hasten its spread and even worsen its lethality. So far, the areas of the world where the most people are dying of the disease – called the case-fatality rate – are densely populated cities in China and Iran.

Recent studies also confirm that air pollution has been blindingly severe in that region of northern Italy where the coronavirus has been most virulent. The Lombardy region and the Po Valley in northern Italy rank among the most air polluted areas of Europe. Similarly, South Korean cities also suffer from levels of air pollution comparable to smoking cigarettes and men there have one of the highest rates of tobacco smoking in the world.