Dear Straight Dope: When I was in 7th grade, I remember reading an article in my science class about a woman who I believe was dubbed "Bloody Mary." The story was that for some reason, she was able to prepare food for herself and not get sick, but when she prepared food for others they were poisoned (a problem, because I believe she worked as a cook or a housekeeper). She went through several families, killing them all, then disappearing and popping up someplace else. I believe they eventually caught her. At any rate, it was found that she had some rare kind of medical condition that caused this phenomenon (not that she simply was poisoning the food). I have never found any mention of this anyplace else, and no one believes me when I tell them about it. I know it wasn't a figment of my imagination. Maybe it was an urban legend, but then why would they teach it in 7th grade science? Elizabeth Thompson, Minneapolis, Minnesota

SDStaff Dex and SDStaff McCaff reply:

It wasn’t “Bloody Mary,” who was someone else entirely, but “Typhoid Mary,” once called “the most dangerous woman in America,” who personally caused at least a dozen outbreaks of typhoid fever. She was born Mary Mallon, around 1870, and Charles Panati calls her a “one-woman epidemic.”

Typhoid fever is caused by Salmonella typhi, a bacillus found in human urine and feces. There are about a thousand strains of salmonella, including the ones responsible for most mild food poisoning. All are transmitted by contact with human or animal waste. Symptoms of typhoid include fever, severe intestinal rumblings, diarrhea, and listlessness. Typhoid has been a major killer for centuries. There were about 215,000 battle deaths during the U.S. Civil War (both sides), but 283,000 deaths from other causes, mostly dysentery and typhoid.

Mary Mallon was a carrier of typhoid. Although it was (and is) widely believed that she herself never became sick with the disease, it’s far more likely that she did become sick and recovered. Regardless, she was a cook in a house in Mamaroneck, N.Y., for less than two weeks in the year 1900 when the residents came down with typhoid. She moved to employment in Manhattan the next year, and members of that family developed fevers and diarrhea, and the laundress died. She went to work for a lawyer, until seven of the eight household members developed typhoid. Mary spent months helping to care for the people she made sick, but of course the contact made many of them worse.

In 1904, she took another position on Long Island. Within two weeks, four of ten family members were hospitalized with typhoid. She changed employment. Three more households infected.

In 1906, the strange outbreaks of cases in New York attracted the suspicion of Dr. George Soper. Typhoid usually strikes in poor, unsanitary conditions; cases among the rich (and sanitary) were unusual. He discovered that the common element was an unmarried, heavyset Irish cook, about forty years old. No one knew her whereabouts. After each case she left and gave no forwarding address. Dr Soper traced her to an active outbreak in a Park Avenue penthouse — two servants were hospitalized and the daughter of the family died.

Soper interviewed Mary, and suggested there might be a connection between the dishes she served and the outbreaks of typhoid. She cursed at him. He requested a stool sample, and she threatened him with a meat cleaver. Finally, police and the New York health commissioner arrested her. She went kicking and screaming.

Under questioning, she said she rarely washed her hands when cooking and felt there was no need — she didn’t consider herself a threat. The woman was in denial — the sheer number of victims argued against this being mere coincidence — but her view wasn’t completely off the wall. Though germ theory had been around since the mid-19th century, it still wasn’t fully accepted, and healthy carriers were definitely an oddity.

Cultures of Mary’s urine and stools (taken forcibly with the help of prison matrons) revealed that her gallbladder was teeming with typhoid salmonella. She refused to have her gallblader extracted or to give up her occupation as cook, maintaining stubbornly that she did not carry any disease. It’is interesting that the state was quite willing to pay for cutting out her gall bladder — an operation that usually had no effect but carried a real risk of killing her — but didn’t even consider disability relief or payments for not cooking.

Authorities labelled her public health enemy number one and confined her to a cottage in the Bronx, where she lived and ate alone. She was effectively imprisoned without trial. She worked at Riverside Hospital as a laundress, swearing that she was the victim of a government conspiracy (no comment).

In 1910, promising to remain a laundress and never return to cooking, Mary was released. She changed her name to Mary Brown and got a job as a cook. For the next five years, she went through a series of kitchens, spreading illness and death, keeping one step ahead of the frustrated Dr. Soper.

In 1915, a serious epidemic of typhoid erupted among the staff of New York’s Sloan Hospital for Women, with twenty five cases and two deaths. City health authorities investigated, learning that a portly Irish-American woman had suddenly disappeared from the kitchen help. The police tracked her to an estate on Long Island. This time she went meekly.

Exactly how many people she infected or killed will never be known. She refused to cooperate with health authorities, withheld information about her past, and used different pseudonyms when she changed cities. Three deaths have been definitely attributed to her, with estimates running as high as 50.

Mary was quarantined for life on North Brother Island. She became something of a celebrity, and was interviewed by journalists (who were forbidden to accept as much as a glass of water from her.) She died in 1938 of pneumonia. It was published at the time that an autopsy revealed that her gallbaldder was still actively shedding typhoid bacilli; however, there is no evidence that an autopsy was actually performed, as attested to in Dr. Soper’s memoirs. (Editor’s note: Grateful thanks to member of the Teeming Millions Phillip Jones, who set us straight.) She was buried by the Department of Health at Saint Raymond’s Cemetery in the Bronx. But her reputation lives on.

SDStaff Dex and SDStaff McCaff, Straight Dope Science Advisory Board

Send questions to Cecil via cecil@straightdope.com.

STAFF REPORTS ARE WRITTEN BY THE STRAIGHT DOPE SCIENCE ADVISORY BOARD, CECIL'S ONLINE AUXILIARY. THOUGH THE SDSAB DOES ITS BEST, THESE COLUMNS ARE EDITED BY ED ZOTTI, NOT CECIL, SO ACCURACYWISE YOU'D BETTER KEEP YOUR FINGERS CROSSED.