Mary Mallon was born on September 23, 1869, a hundred and fifty years ago. An Irish-American, was first person in the US known to be an asymptomatic carrier, and became known as “Typhoid Mary”.

Mallon worked as a cook, unknowingly passing the disease onto people in seven homes she worked for. Each time an outbreak happened, she left to avoid the outbreak, not knowing she was the source. After an investigation she was detained and quarantined at Riverside Hospital on North Brother Island for three years. She fought a legal battle to be released because she had not intentionally committed a crime. In February 1910, Mallon was released under agreement, signing an affidavit, that she never work as a cook again and begin regular hygienic precautions (washing, etc.) to protect others.

Mallon could only find work cleaning laundry, a job that did not pay as well as cooking. After a few years, she changed her name to Mary Brown and broke her agreement, returning to work as a cook and causing several more outbreaks. She was captured and quarantined again in March 1915, this time never to be released. She died at the hospital in 1938.

Mallon’s case was a key moment in the science of bacteriological epidemiology, as the first (or one of) case of an immune carrier of a disease, the investigation and tracking of infectious diseases, and changes in washing and hygiene standards.