Exactly how many people Mary Mallon infected with Typhoid Fever will never be known. Estimates range into the hundreds. At least five deaths (but almost certainly scores more) have been attributed to her.
Throughout her life, Mary Mallon claimed she was unjustly persecuted, and refused to cooperate with authorities at all.
One of the difficulties in determining Typhoid Mary's history was her habit of frequently changing employers, using pseudonyms, and moving from location to location. Thus, it is impossible to know if she was the vector for Typhoid Fever outbreaks in other cities and states.
Her New York area history is reasonably well-documented at least after 1900. Shortly after arriving in New York, she went to work as a domestic. Eventually, she discovered she had skills as a cook, and apparently very fine ones, which gave her a good income for the time. Exactly when she became a cook is uncertain. However, in 1900, she began working as a cook for a family in Mamaroneck, New York. Within two weeks, everyone in the family developed fevers and morbid diarrhea. Mary moved on to another job, and then another.
In 1901, Mary went to work for a family in Manhattan. There was a typhoid outbreak in the home. One person died. Mary moved on again, taking another job, where ten of eleven family members came down with typhoid. Yet again, Mary moved on. In every place where she took employment, Typhoid Fever followed in her wake.
In 1906, she was hired by the noted New York City attorney, Charles Henry Warren, to work as a cook in the family's summer house in Oyster Bay, on Long Island. The entire family took ill. Leaving the Warrens, she worked for other Oyster Bay families, and sickness spread throughout the town. There were several deaths. This was really the first conclusive evidence that Mary Mallon was involved in the outbreaks, since Typhoid Fever was uncommon in Oyster Bay as opposed to the much grimier city of New York.
A private investigator hired by several Oyster Bay families tracked Mary down to a Park Avenue address, where she was working as a cook, and where (unsurprisingly) family members were ill and one had died of Typhoid Fever. Utterly convinced now that Mary Mallon was the common link, he tried to get her to turn herself over to the Public Health authorities. She refused, and moved on again --- and again, Typhoid Fever broke out where she was working.
The Private Investigator wrote of their meeting:
I was as diplomatic as possible, but I had to say I suspected her of making people sick and that I wanted specimens of her urine, feces and blood. It did not take Mary long to react to this suggestion. She seized a carving fork and advanced in my direction. I passed rapidly down the long narrow hall, through the tall iron gate . . . and so to the sidewalk. I felt rather lucky to escape.
New York City officials arrested her in 1907, and quarantined her at their Infectious Disease facility in Riverside Hospital on lonely North Brother Island in the East River. In interviews, an angry Mary refused to accept that there was any problem at all. She said she did not believe in "germs," that handwashing was not necessary in her work, and that she was being persecuted. However, cultures of her bile, urine, and stool were alive with the typhoid bacterium. It was suggested she have her gall bladder removed. She refused.
She came out fighting and swearing, both of which she could do with appalling efficiency and vigor. I made another effort to talk to her sensibly . . . but it was of no use. By that time she was convinced that the law was wantonly persecuting her, when she had done nothing wrong. She knew she had never had typhoid fever; she was maniacal in her integrity.
Many people were outraged that Mary had been bodily carried off by the police, and she became a sympathetic figure and a cause celebre of civil libertarians. "How was she supposed to know she was sick?" they asked, and it was a good question. She was released from North Brother Island in 1910, on condition that she not work as a cook.
When finally found working as a family cook on the North Shore of Long Island, she was arrested and re-quarantined, this time for the rest of her life. She died in 1938 on North Brother Island.
She wrote a sad letter to the authorities during her quarantine:
This contention that I am a perpetual menace in the spread of typhoid germs is not true . . . I am an innocent human being. I have committed no crime and I am treated like an outcast --- a criminal. It is unjust, outrageous, uncivilized. It seems incredible that . . . a defenseless woman can be treated in this manner.
Modern-day commentators have been critical of the roughshod way Mary was treated, and the lack of Due Process in her case. However, it is fairly clear that neither Mary nor the authorities fully understood her condition, and that Mary, at least, was in violent denial of it, refusing any treatment. Given the relatively crude state of medical science in 1900, and Mary's inflexible insistence on working as a cook, it is a matter for debate what could have been done to protect the public weal and Mary's rights as well.