On March 27, 1915, New York City health officials quarantined the 45-year-old woman known as “Typhoid Mary” for the second time after linking her to another typhoid fever outbreak. A century later, the name “Typhoid Mary” remains well known, but the details about her life are not. Check out 10 surprising facts about one of history’s most famous infectious disease carriers.

1. Her real name was Mary Mallon.
She was born on September 23, 1869, in Cookstown, a small village in the north of Ireland. Mallon’s hometown in County Tyrone was among one of Ireland’s poorest areas.

2. Only three confirmed deaths were linked to Typhoid Mary.
Mallon was presumed to have infected 51 people, and three of those illnesses resulted in death. Since she used a number of aliases, it’s possible that the true death toll could have been higher. However, based on the confirmed fatalities, Typhoid Mary was not even the most lethal carrier of the typhoid germ in New York City’s history. In 1922, New Yorker Tony Labella reportedly caused two outbreaks that combined for more than 100 cases and five deaths.

3. She emigrated from Ireland as a teenager.
Mallon traveled by herself to start a new life in the United States in 1883. The teenager moved in with her aunt and uncle in New York City, and even as an adult Mallon never lost her lilting brogue.

4. Typhoid Mary was the picture of health.

Illustration of Typhoid Mary breaking skulls into a skillet, circa 1909. (Credit: Fotosearch/Getty Images)
Illustration of Typhoid Mary breaking skulls into a skillet, circa 1909. (Credit: Fotosearch/Getty Images)

Although she harbored the extremely contagious bacteria that cause typhoid fever, Mallon never demonstrated any of its symptoms—which include fever, headaches and diarrhea. Immune to the disease herself, Mallon was the first person in the United States identified as an asymptomatic carrier of the pathogen. “She denied ever having been sick with the disease, and it is likely she never knew she had it, suffering only a mild flu-like episode,” writes Judith Walzer Leavitt in her book “Typhoid Mary: Captive to the Public’s Health.” “The case is without parallel in medical records,” the San Jose Evening News reported in 1907. “Never has there been an instance, as the present, where a woman who never had typhoid fever should prove a veritable germ factory”

5. She spread disease as a cook for affluent families.
Like many single women who emigrated from Ireland, Mallon found work in America as a domestic servant. Perhaps fitting given her birth in a hamlet named Cookstown, she proved adept in the kitchen and cooked for some of New York City’s most elite families.

6. A sleuthing sanitary engineer tracked down Typhoid Mary.
When six members of wealthy banker Charles Warren’s household contracted typhoid fever while vacationing in Long Island’s Oyster Bay in the summer of 1906, the tony playground of New York’s rich and famous—and home to Theodore Roosevelt’s Summer White House—was taken aback. Typhoid fever was viewed as a disease of the crowded slums, associated with poverty and the lack of basic sanitation. Concerned that the outbreak would prevent him from leasing out his summer house again, Warren’s landlord hired George Soper, a freelance sanitary engineer who had investigated other sources of typhoid fever outbreaks, to determine the cause. Although everything from the house’s plumbing to the local shellfish supply came up negative, the dogged Soper found the cause—Mallon, the cook who had worked for the Warrens weeks before the outbreak. Soper researched Mallon’s employment history and found that seven families for whom she had cooked since 1900 had reported cases of typhoid fever, which had resulted in the infection of 22 people and the death of one girl.

7. A combination of peach ice cream and Mallon’s poor hand washing likely sparked typhoid fever outbreaks.

Mary Mallon in her hospital bed on North Brother Island, New York. (Credit: Bettmann/Corbis)
Mary Mallon in her hospital bed on North Brother Island, New York. (Credit: Bettmann/Corbis)

Doctors theorized that Mallon likely passed along typhoid germs by failing to vigorously scrub her hands before handling food. However, since the elevated temperatures necessary to cook food would have killed the bacteria, Soper wondered just how Mallon could have transferred the germs. He found the answer in one of Mallon’s most popular dessert dishes—ice cream with raw peaches cut up and frozen in it. “I suppose no better way could be found for a cook to cleanse her hands of microbes and infect a family,” Soper wrote.

8. William Randolph Hearst may have bankrolled Typhoid Mary’s suit for freedom.
Based on Soper’s sleuthing, the New York City Health Department took Mallon into custody in 1907 and placed her into forced confinement inside a bungalow on 16-acre North Brother Island, off the Bronx shoreline, with only a fox terrier as a companion. “I never had typhoid in my life and have always been healthy,” Mallon wrote. “Why should I be banished like a leper and compelled to live in solitary confinement with only a dog for a companion?” Armed with test results from a private laboratory that came up negative, Mallon in 1909 sued the health department for her freedom, but the New York Supreme Court denied her petition. Where did Mallon get the money to hire a lawyer and pay the legal bills? Leavitt says speculation has fallen on newspaper magnate William Randolph Hearst, who “had done so for other people whose stories interested his newspaper’s readers.” In 1910, new health commissioner Ernst Lederle agreed to release Mallon if she pledged never to work as a cook again.

9. She broke her promise to stay out of the kitchen.

Poster warning of the dangers of food contamination. (Credit: Otis Historical Archives/National Museum of Health & Medicine)
Poster warning of the dangers of food contamination. (Credit: Otis Historical Archives/National Museum of Health & Medicine)

In 1915, an outbreak of typhoid fever at Manhattan’s Sloane Maternity Hospital struck 25 workers and killed two. The epidemic was traced to the hospital’s cook, whom the staff had nicknamed “Typhoid Mary.” Little did they know that it actually was Mallon, who had taken the assumed name of “Mary Brown.” The health department had lost track of Mallon after her release, during which time she cooked in hotels, restaurants and institutions. After her capture, Mallon was once again confined to North Brother Island.

10. Typhoid Mary spent 26 years in forced isolation.
After her second apprehension, Mallon spent the last 23 years of her life as a virtual prisoner in forced isolation, adding to the three years from her first stint on North Brother Island. Although hundreds, if not thousands, of asymptomatic carriers who had been identified walked the sidewalks of New York freely, Typhoid Mary alone lived in exile in large part due to the public opinion that turned firmly against her after her failure to stay out of the kitchen. She was fated to cook only for herself until her death on November 11, 1938.