Mary Mallon, also known as "Typhoid Mary," was an Irish immigrant to the United States who became the first person identified as a carrier of Salmonella typhi, the bacteria that causes typhoid fever. Born in 1869, she worked as a cook in New York City and unknowingly infected several people with the disease, leading to outbreaks in the early 1900s. In 1907, health authorities discovered her role in the spread of typhoid fever and quarantined her for several years. Despite her protests, she remained a significant figure in public health discussions about asymptomatic carriers and the importance of hygiene in preventing disease transmission.