Mary Mallon - Wikipedia

On June 15, 1907, Researcher George Soper publishes the results of his investigation into recent typhoid outbreaks in the New York area and announces that Mary Mallon [Typhoid Mary] is the likely source of the outbreak.". From the article:
"In late 1906, one family hired a typhoid researcher named George Soper to investigate. Soper published the results on June 15, 1907, in the Journal of the American Medical Association. He believed Mallon might be the source of the outbreak.[9] He wrote:

"It was found that the family changed cooks on August 4. This was about three weeks before the typhoid epidemic broke out. She remained in the family only a short time, leaving about three weeks after the outbreak occurred. The cook was described as an Irish woman about 40 years of age, tall, heavy, single. She seemed to be in perfect health."

Soper discovered that a female Irish cook, who fit the physical description he was given, was involved in all of the outbreaks. He was unable to locate her because she generally left after an outbreak began, without giving a forwarding address. Soper learned of an active outbreak in a penthouse on Park Avenue, and discovered Mallon was the cook. Two of the household's servants were hospitalized, and the daughter of the family died of typhoid.[8]

When Soper approached Mallon about her possible role in spreading typhoid, she adamantly rejected his request for urine and stool samples.[10] Since Mallon refused to give samples, he decided to compile a five-year history of Mallon's employment. Soper found that of the eight families that hired Mallon as a cook, members of seven claimed to have contracted typhoid fever.[11] On his next visit, he brought another doctor with him but again was turned away. During a later encounter when Mallon was herself hospitalized, he told her he would write a book and give her all the royalties. She angrily rejected his proposal and locked herself in the bathroom until he left."