Mary Mallon (1869-1938) was an Irish immigrant who worked as a cook for rich families in New York. She was responsible for several outbreaks of typhoid fever since she was an asymptomatic carrier of Salmonella typhi. Because of the danger and fear for new outbreaks, she was held in quarantine for years, against her will. What factors contributed to this decision? Was it necessary to keep her isolated? And what was the role of public opinion and media? The history of Mary Mallon is a sad and tragic chapter in medical history, from which we can still draw important lessons.