We have been hearing about “asymptomatic carrier” quite a lot in the past few months. It scares us to death that there are people carrying chronic diseases with no outward symptoms of the microbes within, spreading the deadly disease to unsuspecting, healthy individuals they come into contact with. But back in the early 1900s, the concept of “healthy carriers” of infection was entirely new to scientists, and this brings us to the story of Mary Mallon, the first known asymptomatic carrier of typhoid in the United States, who is believed to have infected more than fifty people with typhoid fever, three of whom died.

An illustration, published around 1909, depicting “Typhoid Mary” breaking skulls into a skillet.