This episode covers the 1951 Nobel Prize in Physiology or Medicine, which was awarded to Max Theiler. The Nobel Assembly at the Karolinska Institute chose to give Theiler the award “for his discoveries concerning yellow fever and how to combat it”. Topics include the discovery that yellow fever is spread by mosquitos, the discovery that yellow fever is caused by a virus, and how Theiler was able to create a live-attenuated vaccine for yellow fever that we still use today.