"Recognize how ignorance accelerates catastrophic spread During the Black Death of the 1300s, the plague killed up to 60 percent of Europe's population in part because people had no scientific understanding of its causes or transmission. Physicians performed bloodletting — cutting open veins to drain blood — believing illness came from a blood imbalance, a practice that killed rather than cured; even George Washington and King Charles II died shortly after receiving this treatment. Recognizing that confident, widely-accepted methods can be catastrophically wrong should make anyone pause before blindly following established consensus in any field, and actively seek evidence of whether a practice actually works. Source: Narrator, The Infographics Show, The Black Death - 47 Million Killed - What Was It Like?"