Young doctor Jesse Lazear has deadly Yellow Fever. He thrashes around and convulses in his sick bed, and his vomit is black. He is just 34 when he dies. Curiously, mosquito expert Lazear was researching the disease when he became ill. Some historians think his infection wasn't an accident, and that he was secretly experimenting on himself... Today, human challenge trials - where volunteers are intentionally given a disease under the watchful eye of medical support - are rare. The authorities are wary of the risks involved. But such trials can also mean that vaccines are developed faster and thousands of lives are saved. Is it time to start thinking differently about experimenting on humans? For a full list of sources, see the show notes at timharford.com.See omnystudio.com/listener for privacy information.