Tracking down the culprit behind an outbreak of typhoid fever in 1900s New York was a breakthrough in how symptom-free carriers can spread sickness.
GEORGE SOPER WAS not your typical detective. He was a civil engineer by training, but had become something of an expert in sanitation. So when, in 1906, a landlord in Long Island was struggling to trace the source of a typhoid outbreak, Soper was called in. The landlord had rented his Long Island house to a banker’s family and servants that summer. By late August, six of the house’s 11 inhabitants had fallen ill with typhoid fever.
Soper had been previously hired by New York state to investigate disease outbreaks—“I was called an epidemic fighter,” he later wrote—and believed that typhoid could be spread by one person serving as a carrier. In Long Island, he focused his attention on the cook, Mary Mallon, who had arrived three weeks before the first person became ill.
What Soper discovered would demonstrate how an unwitting carrier could be the root of disease outbreaks, and, later, spark a debate about personal autonomy when it’s pitted against public health.
Combing through the roster of wealthy New Yorkers who had employed Mallon in their summer homes between 1900 and 1907 he found a trail of 22 infected people. Typhoid fever is a bacterial infection typically spread through food and water contaminated by salmonella. Patients fall ill with high fever, diarrhea—and, before antibiotics were developed to treat it, sometimes delirium and death.
At that time, without regulated sanitation practices in place, the disease was fairly common and New York had battled multiple outbreaks. In 1906, the year Soper began his investigation, a reported 639 people had died of typhoid in New York. But never before had an outbreak been traced to a single carrier—and certainly not one without any symptoms themselves.
Soper learned that Mallon would often serve ice cream with fresh peaches on Sunday. Compared to her hot, cooked meals, he deduced that “no better way could be found for a cook to cleanse her hands of microbes and infect a family.”
Hunting the carrier
Four months after he started the investigation, Soper found Mallon working in a Park Avenue brownstone. The 37-year-old Irish cook, he later described, was “five feet six inches tall, a blond with clear blue eyes, a healthy color and a somewhat determined mouth and jaw.” When confronted with his evidence and a request for urine and feces samples, she surged at Soper with a carving fork.
Dr. S. Josephine Baker, an up-and-coming advocate of hygiene and public health, was dispatched to convince Mallon to provide samples, but was also chased away. Baker, whose father had died of typhoid, later made it her mission to promote preventative medicine (and became the first woman to earn a doctorate in public health). “It was Mary’s tragedy that she could not trust us,” Baker later wrote.
Finally, Mallon was escorted by Baker and five policemen to a hospital where—after a nearly successful escape attempt—she tested positive as a carrier for Salmonella typhi, a bacteria that causes typhoid. This would later be confirmed by more tests. She was quarantined in a small house on the grounds of Riverside Hospital. The facility was isolated on North Brother Island, a tiny speck of land off the Bronx.
Mallon herself had no symptoms of typhoid and didn’t believe she could be [ … ]