Typhoid Mary

 this is an illustration that appeared in The New York American (1909, 20 of June)

Mary Mallon (September 23, 1869 – November 11, 1938), better known as Typhoid Mary, was the first person in the United States identified as an asymptomatic carrier of the pathogen associated with typhoid fever. She was presumed to have infected some 50 people, three of whom died, over the course of her career as a cook. She was forcibly isolated twice by public health authorities and died after a total of nearly three decades in isolation.

Exactly how many people were infected or killed by her is not known. She refused to cooperate with health authorities, withheld information about her past, and used different pseudonyms when she changed cities. Three deaths have been definitively attributed to her, with estimates running as high as 50. Mallon was the first healthy typhoid carrier to be identified by medical science, and there was no policy providing guidelines for handling the situation. Some difficulties surrounding her case stemmed from Mallon's vehement denial of her possible role, as she refused to acknowledge any connection between her working as a cook and the typhoid cases. Mallon maintained that she was perfectly healthy, had never had typhoid fever, and could not be the source. Public-health authorities determined that permanent quarantine was the only way to prevent Mallon from causing significant future typhoid outbreaks.

A historical poster warning against acting like Typhoid Mary

Today, Typhoid Mary is a generic term for anyone who, knowingly or not, spreads something undesirable. In August 2013, researchers at the Stanford University School of Medicine announced they were making breakthroughs in understanding the exact science behind asymptomatic carriers such as Mary. The bacteria that causes typhoid may hide in macrophages, a type of immune cell.

Individuals can develop typhoid fever after ingesting food or water contaminated during handling by a human carrier. The human carrier may be a healthy person who has survived a previous episode of typhoid fever yet who continues to shed the associated bacteria, Salmonella typhi, in feces and urine. Washing hands with soap before touching or preparing food, washing dishes and utensils with soap and water, and only eating cooked food are all ways to reduce the risk of typhoid infection.

Read all her story in wikipedia