Mary Mallon, American cook and typhoid carrier (died 1938)

Mary Mallon, commonly known as Typhoid Mary, was an Irish-born American cook who is believed to have infected between 51 and 122 people with typhoid fever. The infections caused three confirmed deaths, with unconfirmed estimates of as many as 50. She was the first person in the United States identified as an asymptomatic carrier of the pathogenic bacterium Salmonella typhi. She was forcibly quarantined twice by authorities, the second time for the remainder of her life because she persisted in working as a cook and thereby exposed others to the disease. Mallon died after a total of nearly 30 years quarantined. Her popular nickname has since become a term for persons who spread disease or other misfortune.

Typhoid fever, also known as typhoid, is a disease caused by Salmonella enterica serotype Typhi bacteria, also called Salmonella Typhi. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over several days. This is commonly accompanied by weakness, abdominal pain, constipation, headaches, and mild vomiting. Some people develop a skin rash with rose colored spots. In severe cases, people may experience confusion. Without treatment, symptoms may last weeks or months. Diarrhea may be severe, but is uncommon. Other people may carry it without being affected, but are still contagious. Typhoid fever is a type of enteric fever, along with paratyphoid fever. Salmonella enterica Typhi is believed to infect and replicate only within humans.

September 23 is the 266th day of the year in the Gregorian calendar; 99 days remain until the end of the year.