This is a very interesting story which I read few days ago. In 1906, a New York banker named Henry Warren was in Long Island, enjoying his vacation. An Irish women called Mary Mallon worked with them as their cook. The women left for some reasons. Within a few week, half of the family members got infected with Typhoid. This was not in accordance to the environment in which they lived, since Typhoid was prevalent in slums amongst poor section, not richer section of society. Further Typhoid can be transmitted only through a carrier, not by a healthy person.
George Sofer, a sanitary engineer investigated the situation. Soon there was an outbreak of typhoid and the only thing common was Mary Mallon. She was an excellent cook but she was a live carrier of Typhoid bacteria. After being detected and caught she spent 3 years in isolation on North Brother Island in New York’s East river. She was released in 1910, when authorities lost her track.
After 5 years there was an outbreak of typhoid at Sloane Maternity Hospital in Manhattan. Investigation revealed that hospital cook, Mrs Brown was none other than Typhoid Mary (Mary Mallon nick name). Later she was sent to North Brother Island again where she stayed forever untill her death in 1938.