Mary...

Mary Mallon also known as Typhoid Mary, was an Irish-American cook. She 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 51 people, three of whom died, over the course of her career as a cook.^[1] She was twice forcibly isolated by public health authorities and died after a total of nearly three decades in isolation.

From 1900 to 1907, Mallon worked as a cook in the New York City area for seven families.^[7]In 1900, she worked in Mamaroneck, New York, where, within two weeks of her employment, residents developed typhoid fever. 

In 1901, she moved to Manhattan, where members of the family for whom she worked developed fevers and diarrhea, and the laundress died. Mallon then went to work for a lawyer and left after seven of the eight people in that household became ill.^[8]

In the year 1906, Mary took a position in Oyster Bay, Long Island, and within two weeks 10 of the 11 family members were hospitalized with typhoid.

She changed jobs again, and similar occurrences happened in three more households.^[8] She worked as a cook for the family of a wealthy New York banker, Charles Henry Warren. When the Warrens rented a house in Oyster Bay for the summer of 1906, Mallon went along, too. From August 27 to September 3, six of the 11 people in the family came down with typhoid fever. The disease at that time was "unusual" in Oyster Bay, according to three medical doctors who practiced there.^{[citation needed]}Mallon was subsequently hired by other families, and outbreaks followed her.