How did her name become synonymous with deadly disease? And who is really responsible for the lasting legacy of Typhoid Mary?

Mary Mallon (better known as Typhoid Mary) emigrated to the United States from Ireland in 1884. She worked for wealthy families in the US before becoming a cook and was a healthy carrier for salmonella typhimurium (or typhoid fever).
In 1906, she worked for a wealthy New York banker who rented a summer home. By late August into early September, six of the eleven people in the house had typhoid fever. George Sober, a sanitary engineer, initially thought clams were the culprit, but not everyone who was ill had eaten them. Meanwhile Mary, who was displaying a moderate form of the disease, denied being sick.
She continued to work for families as a cook, contaminating everything in her wake and presenting a threat to those around her. Sober began following Mary around Manhattan and realizing that her work and daily activities were both spreading disease and death.
3,000 New Yorkers were infected that year, and Mary is accredited with being the reason for that large outbreak. At that time, immunization for typhoid fever didn't exist (and wouldn't exist until 1911, with antibiotic treatment being unavailable until 1948). Thus, Sober and the Department of Health had to resort to quarantine.
Mary was freed from quarantine in 1910 by a health commissioner who wanted to find her diligent work outside of the cooking industry. Mary agreed but never intended to follow through on her word, returning to work as a cook once more for wealthy families and threatening the health of the public. In the three months following, she contaminated at least 25 people and earned the stigma of Typhoid Mary. She was placed back in quarantine until her death.
The name "Typhoid Mary" began showing up in medical dictionaries to describe a disease carrier. During the course of her career, she was found directly responsible for the contamination of at least 122 people. By the time of her death, 400 other healthy carriers of typhoid disease had been identified.
It's likely that the initial fear of the work she was doing and the fact that her nickname had begun to show up in medical dictionaries and everyday conversation is the cause of her legacy. The stigma around disease, outbreaks, and fear have contributed to the way we regard Mary Mallon. After all, no one talks of those other carriers as "Typhoid ____."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3959940/