North Brother Island is a 16.5-acre bump of land jutting out of the East River, 1,500 feet east of 140th Street in the South Bronx and 2,500 feet west of Riker’s Island. Once the site of New York City’s lazaretto, or quarantine hospital, it is now a favorite nesting point for herons and egrets. In its long career as an agent of quarantine, however, North Brother Island deserves mention as the enforced residence of New York City cook Mary Malone, or as she was better known, “Typhoid Mary.”

In 1884, Mallon emigrated from Tyrone County in Ireland to the United States. She was only 15. Mary earned her income as a domestic and a cook in the New York City area. Between 1900 and 1907, she infected many people with Salmonella typhosa — then the name for the causative organism of typhoid fever. Less understood to doctors of the time—and explicated so nicely through Mary Malone’s case–was that salmonella carriers can be completely asymptomatic while still spreading the germ, which tends to harbor in a person’s gall bladder. Modern bacteriology dictates that the microbe sheds in feces and urine, demanding excellent hand washing, especially before preparing food, to cut down on the spread.

An intrepid New York City Health Department epidemiologist named George Soper tracked down a spate of typhoid cases that began in a Park Avenue penthouse where Mary worked. Dr. Soper demanded she turn over urine and stool samples, but Mary refused. As his investigation continued, Soper discovered that of eight families Mary had previously worked for as a cook, seven of them had experienced bouts of typhoid fever. Soper made many more entreaties to Malone, all for naught. Once when she was hospitalized he even promised to write a book about her and give her all the royalties. Still, Mary refused to cooperate, insisted that she had done nothing wrong, and complained that she was being persecuted by the City of New York. In 1907, city officials arrested her in the name of the public’s health. More than one newspaper reported she was “crawling with typhoid bugs.” But it was the Journal of the American Medical Association, in a 1908 issue, that is credited with coining the now famous epithet, “Typhoid Mary.”

The New York City health department physicians gave her an ultimatum: submit to an operation to remove her gall bladder or be imprisoned on the lazaretto. Abdominal surgery of that era was fraught with deadly complications and infections and Mary understandably rejected such a choice. The officials then, literally, sent her up the river to North Brother Island, where, under sections 1169 and 1170 of the Greater New York City Charter, she lived in a tiny brick bungalow until she was released in 1910.

One of the conditions of her freedom was a promise that she would no longer earn her income working as a cook. Initially Mary worked as a laundress. But soon enough, to make ends meet, she took on kitchen jobs against doctor’s orders. The result were still more outbreaks of the deadly typhoid.

On March 27, 1915, the New York City Sanitary Police tracked her down, this time on a Long Island estate. Mary Malone was confined to North Brother Island, never to return to a normal or free life. She resided there until her death, at age 69, in 1938. One of her “jobs” there was to wash the bottles and glassware used in the quarantine hospital’s laboratory. Upon her autopsy, the pathologist diagnosed evidence of live typhoid bacilli in her gall bladder.

“Typhoid Mary” lives on in the popular culture because the very name conjures a personification of a spreading epidemic or contagious crisis. Perhaps more important, Mary’s case history introduced physicians to the concept of a carrier state, whereby seemingly healthy people can spread typhoid fever as they harbor the disease-producing microbe in their bodies without apparent harm to themselves.

As we mark the day in medical history when Mary Malone received her life sentence, however, it is worthwhile reflecting on how harshly public health officials once handled those deemed a contagious threat to others. And what a terrible life sentence it must have been. A little less than century later, standing on the rocky shoals of the island, peering into the distance, the city seems remote and inaccessible. From Mary’s perspective of forced isolation for more than 30 years, it must have been truly painful.

Dr. Howard Markel writes a monthly column for the PBS NewsHour, highlighting the anniversary of a momentous event that continues to shape modern medicine. He is the director of the Center for the History of Medicineand the George E. Wantz Distinguished Professor of the History of Medicine at the University of Michigan.

He is the author or editor of 10 books, including “Quarantine! East European Jewish Immigrants and the New York City Epidemics of 1892,” “When Germs Travel: Six Major Epidemics That Have Invaded America Since 1900 and the Fears They Have Unleashed” and “An Anatomy of Addiction: Sigmund Freud, William Halsted, and the Miracle Drug Cocaine.”

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Do you have a question for Dr. Markel about how a particular aspect of modern medicine came to be? Send them to us at onlinehealth@newshour.org.