It began with a tweet: “EVERY DAY IS IGNAZ SEMMELWEIS DAY.” Carl Zimmer — tweet author, acclaimed science writer and friend of the show — tells the story of a mysterious, deadly illness that struck 19th century Vienna, and the ill-fated hero who uncovered its cure … and gave us our best weapon (so far) against the current global pandemic.

This episode was reported and produced with help from Bethel Habte and Latif Nasser.

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