Stubbins Ffirth’s Test of Yellow Fever’s Contagion
In the early 19th century, physician Stubbins Ffirth wanted to know whether yellow fever passed directly from one person to another. The practical stakes were serious: if contact spread the disease, caring for patients or handling their belongings could put others at risk. Ffirth tested that possibility on himself, drinking patients’ vomit and applying it to cuts in his skin.
The experiments were extreme, but they reflected a real uncertainty. Doctors could observe who became ill and when; they could not yet identify the virus or the route by which it reached people. Ffirth’s tests targeted bodily fluids as a possible means of transmission. He did not develop yellow fever, and the results supported his conclusion that contact with vomit was not enough to transmit it.
What His Results Could—and Could Not—Show
A failed attempt to cause disease is evidence about the route tested, not proof that yellow fever had no infectious cause. Ffirth’s experiments did not reveal how the illness actually spread. That distinction matters: yellow fever is caused by a virus, but it is transmitted mainly through the bite of infected mosquitoes, not by drinking a patient’s vomit or touching it through a wound.
Ffirth’s work is striking because it shows how physicians tried to answer a life-or-death question before they knew about viruses or mosquito transmission. His self-experiment helped rule out one suspected route, but the decisive clue lay outside the sickroom: the insect carrying the disease from person to person.
