Who Was Typhoid Mary And How Did She Spread Typhoid?

Mary Mallon, famously known as Typhoid Mary, was an asymptomatic carrier of the typhoid bacterium. She spread typhoid to the residents the houses she worked at and caused a lot of deaths.

In the summer of 1906, Charles Henry Warren, a prosperous New York banker, rented a comfortable residence in the scenic town of Oyster Bay, New York. What made the house even more special was the presence of an excellent cook, whose peach ice cream was simply to die for. 

What Mr. Warren, his three family members, and seven servants could not have imagined was that this decadent ice cream would end up making them sick. More than half of their household caught typhoid fever, which led to the discovery of the first identified carrier of typhoid in any English-speaking country: Ms. Mary Mallon, also known as Typhoid Mary.

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In The Times Of Typhoid

However, before we dive into Mary Mallon’s life and legend, let’s attempt to better understand what typhoid is and how it spreads, and what it meant to be sick with typhoid fever in the early 1900s. 

Typhoid fever, also known as enteric fever, is caused by the bacterium Salmonella typhi (S. typhi). They look like microscopic Tic Tacs (rod-shaped), with tiny string-like structures, called flagella, radiating out of their body. The flagella flaps around, which helps the bacteria move.


Salmonella typhi (Photo Credit : Festa/Shutterstock)

But how do these bacteria get inside our bodies?

Microorganisms that cause disease (pathogens) need to have a place to stay and multiply, known as a reservoir. At some point, you might have been rushed to the hospital after a particularly bad cut while playing outside in order to get a tetanus shot. That’s because the bacteria that causes tetanus, Clostridium tetaniuses soil as their reservoir. 

For S. typhi, the human body is the reservoir. This means that it is through the human body that the disease spreads, specifically through the fecal-oral route

Typhoid generally exists and sustains in areas with exceedingly poor hygiene. It enters the human body when a person ingests food or water contaminated by an infected person who has not washed their hands or followed proper sanitary measures.

The symptoms of typhoid manifest in high fever, stomach pain, a rosy rash, and loss of appetite.

Typhoid Fever Unhygienic Lifestyle Poor Sanitation Stick Figure Pictogram Icons

Causes and Symptoms of Typhoid (Photo Credit : Leremy/Shutterstock)

These symptoms, however uncomfortable, do not pose a mortal threat in today’s day and age. 

But back in the early 1900s, they definitely did.

Nearly 20% of individuals suffering from typhoid fever succumbed to it in 1906. As mentioned earlier, S. typhi utilizes the human body as its abode, so the number one spreader of the disease is an infected person. However, back in the day, people were so afraid of affliction that they would take proper measures to quarantine individuals who contracted typhoid.

The question is, how do you protect yourself from a person who appears completely healthy, but carries the pathogen?

How Mary Mallon Came To Be Known As Typhoid Mary

Mary Mallon was born in Ireland in 1869 and migrated to the United States in the 1880s for better employment opportunities. Owing to her better-than-average culinary skills, she soon found paying work as a cook for well-off families in New York.

Also Read: Who Was Robert Koch And What Are Koch’s Postulates?

Mary could have gone on cooking for wealthy New York families while living a relatively ordinary yet comfortable life, had she not been harboring a deadly disease.

Mary was an asymptomatic carrier of S. typhi, which signifies an individual who carries the pathogen of a particular disease, but does not demonstrate any symptoms of the given disease.

An individual is said to be asymptomatic when they are infected with a pathogen, but show none of its signs or symptoms. Other infections that might present asymptomatically in a small percentage of people are cholera, HIV, the common cold, and tuberculosis. 

These asymptomatic carriers are pretty frequent, however, and won’t go down in history like Typhoid Mary.

Mary was one of the first asymptomatic carriers discovered in the United States. There had probably been thousands like her who were super-spreaders of typhoid fever back in the 20th century, but no one realized this fact. Almost 2% to 5% of people who have once contracted typhoid end up becoming carriers of the disease.

Typhoid carrier polluting food

An Artistic Depiction of Typhoid Mary. (Photo Credit : Otis Historical Archives Nat’l Museum of Health & Medicine/Wikimedia commons)

When a foreign body enters our body, our immune system, like frontline warriors, fights them off. Sometimes our immune system is not fully able to wipe out an entire load of pathogens. The minute percentage that remains behind does not cause the individual any apparent harm, but makes them carriers of the disease. 

After the Warren household fell ill, the owner of the residence, out of fear that no one would rent her place owing to disease, employed a successful sanitation engineer, George Soper, to track down the cause of the outbreak. Having exhausted all other options, Soper finally turned his attention to the cook, who by then was no longer working in the house. He traced Mary’s work history and found that all seven households where Mary had once worked had experienced typhoid breakouts.

When Mary was approached by Soper and other healthcare authorities for a checkup, she vehemently opposed it. Mary would maintain this uncooperative behavior towards healthcare officials for the next half decade.

Eventually, she was taken to a quarantine center and tested, and was found positive for S. typhi. 

She transferred to a serene hospital in North Riverside, where she remained confined for two years. In two years, 120 of Mary’s stool tests (out of 163 taken) tested positive for typhoid-causing bacteria.

During this time, the doctors concluded that the primary hub of S. typhi in her body was in the gall bladder and offered her the option of having it removed so that she could live without worrying about infecting others with typhoid.

Mary Mallon

The Authentic Stool Report of Mary Mallon, dated 1907. (Photo Credit : Jtamad/Wikimedia commons)

Mary refused, and after two years, she was let go from the hospital on the condition that she would abide by proper hygiene and not work as a cook again.

Mary flouted all the conditions, and in five years, after causing a few more mini-outbreaks of typhoid, she was permanently quarantined in the hospital in North Riverside for the rest of her life. 

Soper’s investigations stated that Mary had caused around 10 outbreaks of typhoid involving 122 cases and 5 deaths. These were the numbers that could be officially traced back to Mary. Soper, however, believed that she might have been responsible for the typhoid epidemic that infected almost 3,000 New Yorkers in 1907. 

Also Read: How Do Scientists Find “Patient Zero” Of A Viral Pandemic?


Typhoid Mary is now synonymous with the most prominent example of an asymptomatic human carrier. Her case, though, in no way solitary, paved the way for breakthroughs in controlling infectious diseases, understanding the behavior of microorganisms within the human body, and revolutionizing the healthcare system. Sanitary measures, such as the chlorination of water, pasteurization of milk, and proper purification protocol of sewage waste were strictly enforced from this point forward. Personal hygiene of those infected with and recovering from typhoid was especially emphasized.

Currently, the world encounters 21 million cases of typhoid each year, mostly in countries with poor access to appropriate sanitation. The primary spreaders of typhoid remain asymptomatic carriers of S. typhi. 

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About the Author

Shreyasi is a Master’s in Neuroscience from Sophia College, Mumbai. Her love for writing about science comes from reading writers such as Richard Dawkins and V. S. Ramachandran. She is especially interested in the interdisciplinary aspect of science and believes anything can be connected & explained scientifically. When she isn’t buried in a book or watching true-crime documentaries, she is found to be taking long walks with the sole purpose of petting every stray cat that crosses her path.