Supplemental File S3: Typhoid Mary case teaching notes
The Case of Typhoid Mary
In the early 1900s, Mary Mallon worked as a cook in New York. At that time, she was known for her peach melba; today she is best known for her ability to spread typhoid fever. Known as “Typhoid Mary”, she has been credited with starting seven epidemics and infecting more than 50 people within a 10 year period. In 1907, she was sentenced to live in an isolated cottage on Brother Island, New York. In 1910, she was released after agreeing to not work as a cook again. However, Mary did take more cooking jobs and continued to cause outbreaks of typhoid including one in a hospital that infected 25 people and killed two. She was tracked down in 1915 while she was working under an assumed name. She was returned to Brother Island and lived out her remaining 23 years in relative isolation. Mary died in 1938 at the age of 69.
In the United States today, there are approximately 5700 cases of typhoid/year; most of these are acquired during international travel. In contrast, typhoid remains a significant health concern in the developing world where about 21 million people/year are affected. The etiologic agent of typhoid is Salmonella enterica subtype Typhi (S. Typhi). Found only in humans, S. Typhi is a Gram-negative motile rod. After ingestion of contaminated food or water, S. Typhi survives passage through the stomach to reach the intestines and establish infection. Infected people carry S. Typhi in their blood and intestine; it is shed via feces. S. Typhi is transmitted to a susceptible host by ingestion of contaminated food or water. Mary Mallon was a lifelong carrier of S. Typhi. While she reported never having typhoid, she shed S. Typhi in her feces until she died.
Approximately 1-2 weeks after ingestion symptoms will appear. During the 1st week, the symptoms are somewhat general--headache, fever, general malaise. Definitive diagnosis can be made by testing blood or stool for S. Typhi. During this stage, patients may feel exhausted and experience a loss of appetite. During the second week, the fever may rise to 104∘F. Patients may experience delirium and about 10% of patients develop a rose-colored rash. The abdomen may become distended; diarrhea or constipation is associated with this stage of infection. Without treatment, the infection will grow more severe and can lead to intestinal perforation and hemorrhage; death occurs in about 20% of cases. Typhoid can be treated with antibiotics and there is a vaccine available. Typhoid can be treated with antibiotics; without treatments, the illness can last 3-4 weeks and death may occur.
Image credits:
S. Typhi image: Public Health Image Library #16877
General Research Division, The New York Public Library. "Typhoid Mary." New York Public Library Digital Collections. Accessed June 5, 2015.
1) Mary Mallon caused 7 epidemics during her lifetime. What is an epidemic? How does it differ from a pandemic or endemic disease?
Epidemic refers to a disease occurring in an area or population at a rate that is higher than usual. It differs from pandemic disease in that a pandemic refers to an epidemic occurring on more than one continent at a given time. Endemic disease is that which occurs at a nearly constant incidence in a given population or area.
Visuals: Image depicting endemic, sporadic, epidemic, and pandemic disease.
Discussion extension: After using visual to reiterate student responses, ask the class to come up with examples for each type of disease frequency.
2) In this case, what was the reservoir of disease?
Mary was the reservoir for the disease.
Visuals: Images of various reservoirs—animals (zoonoses), humans, nonliving (water, food, soil).
Discussion extension: Ask students to come up with examples for each type of reservoir. What are some of the challenges for controlling diseases with the various reservoirs?
3) Mary’s job as a cook facilitated transmission of the typhoid to others. The transmission of typhoid via food represents what mode of transmission? What would be the portal of entry? What was the portal of exit?
Foodborne transmission is a form of vehicle transmission. The portal of entry was the mouth and exit was the anus (feces).
Visuals: Images of modes of transmission (vehicle, vector, direct contact, indirect contact) and images of portals of entry and exit.
Discussion extension: Briefly cover portals then show transmission modes and discuss likely portals of entry and exit for each. For example, vehicle transmission images could include aerosols, water, food, and bodily fluids. Aerosol entry and exit are likely via mouth, nose, and eyes. Water and food are likely mouth or nose entry and exit via the anus or secretions. Bodily fluids entry and exit likely via mouth, vagina, or anus.
4) S. typhi produces a variety of adhesins including multiple types of fimbriae. Why are adhesins important in pathogenesis?
Adhesins are important because they mediate the initial interactions of a pathogen with the host.
Visuals: Image of a bacterium interacting with a host cell; emphasize the ligand/receptor interactions that occur.
Discussion extension: What types of molecules could function as adhesins? If you had a strain of S. Typhi with mutated fimbriae do you think it would be as effective at causing disease as the wild type strain?
5) What is the relationship between the terms pathogenicity and virulence?
Pathogenicity refers to the ability of an organism to cause disease and virulence refers to the degree of pathogenicity.
Discussion extension: Pose a thought question to students—“could a pathogen be highly virulent and cause mild disease?” or “can you think of a situation where a less virulent organism could cause significant disease?” This opens the discussion to clarify virulence as the degree of pathogenicity and the concept of a virulence continuum. Also allows for clarification that virulence and pathogenicity do not explain the severity of disease.
6) Like all pathogens, S. typhi produces a variety of virulence factors during infection. What are virulence factors? Provide 2 general examples of virulence factors.
Virulence factors are traits that contribute to an organism’s ability to cause disease. Examples include enzymes, toxins, antiphagocytic factors.
Visuals: Images of basic virulence factors—extracellular enzymes (hyaluronidase, collagenase, coagulase); exotoxins and endotoxin; antiphagocytic factors.
Discussion extension: Options: 1) Compare 2 pathogens, their “palettes” of virulence factors and their ability to cause disease. Examples: S. Typhi and P. aeruginosa. 2) Relate virulence factor production to clinical outcomes. Examples: E. coli and endotoxic shock. 3) Relate to experimental example such as Griffith’s classic experiments demonstrating the role of capsule in virulence.
7)Draw a graph showing the course of the disease and the relative number of S. typhi over time. Label the five stages of the disease on your graph. Hint: the case provides you information about the progression of the disease—use this to guide you!
1: Incubation
2: Prodromal
3: Illness
4: Decline
5: Disease
Discussion extension: Discuss the pieces from the narrative that correspond to each stage. Why does the period of illness correspond to the greatest number of bacteria? What factors impact the length of each stage?
After listening to the RadioLab story and reading the NY Times article, answer the following:
8) Describe George Soper’s approach in determining the cause of the typhoid outbreaks. A flow chart of his steps might be an effective way to approach this.
Soper called to Warren vacation home in Oyster Bay
↓
Soper reviews findings from earlier investigators.
Questions household members and compiles a list of visitors for the past 10 years
↓
Examines medical records of all visitors
↓
Discovers that a couple weeks before the outbreak the Warrens hired a new cook.
That cook is now missing!
↓
Goes to employment agency and determines cook’s previous employers. Finds out that in every household where she worked there had been a typhoid outbreak
↓
Tracks Mary Mallon down at a home where she is working as a cook. Confronts her demanding blood, urine, and feces samples. Mary “comes at him” with a serving fork!
↓
Soper enlists the help of S. Josephine Baker in getting the samples from Mary. Baker is met with same resistance as Soper. Baker gets the police involved
Visuals: Generate the flow chart using step-by-step input from students. Can be done as a powerpoint slide or on a whiteboard, chalkboard, etc.
Discussion extension: Ask students questions as the flow chart develops. Why was it important that Soper reviewed all the records of the earlier investigators? Why were people surprised that the outbreaks were occurring in well-to-do families? Why was Mary so enraged when confronted by Soper and Baker?
9) What type of epidemiological study was Soper conducting?
Soper was conducting a descriptive study.
Visual: The visual was generated during the discussion of this question.
Discussion extension: Ask students why Soper’s study was descriptive. A powerpoint slide can be generated during the discussion to outline the characteristics of a descriptive study. (This could also be done on a whiteboard or other visual device). Then ask students what the other types of epidemiological studies are and list the characteristics of each type. What are the benefits of each type of study? In other words, how does each contribute to the public health response to disease?
10) How does the work that Soper was doing differ from etiology?
Etiology studies the causation of disease whereas epidemiology studies where and when diseases occur and their transmission.
Visuals: Image of Koch’s postulates
Discussion extension: Contrast the work that Soper did with that of Koch. Draw attention to the fact that Soper wasn’t looking for causative agent, he was looking for where the disease was occurring and how it was being transmitted. Koch was looking to identify the causative agent, he didn’t focus on transmission or the time and place of infection.
11) Based on the RadioLab piece, you know that Mary was not the only person that was identified as a carrier in New York. So why was Mary the only one quarantined on Brother Island? Why is she the only one that we talk about today? Judith Leavitt, author of Typhoid Mary and guest in the RadioLab piece, thinks that there was prejudice against Mary for being Irish and a woman, and also for being a domestic servant, not having a family, not being considered a "bread earner," having a temper, and not believing in her carrier status. What do you think? Pay attention to the historical context—we are talking about events that occurred in the early 1900’s, not the present day.
Discussion extension: The discussion will be student-directed based on their answers. Some additional questions instructors might ask to further stimulate discussion include: What do you think about the fact that Mary went back to work as a cook after her initial release from Brother Island? What were the employment “options” for an unmarried women at the time? What do you think about the fact that other carriers of typhoid were identified but none were sentenced to Brother Island like Mary even though some of them (mostly males) were working as cooks? Do you think Mary’s imprisonment was, as Jad Abumrad suggests, to make people feel safe?
Sources:
Leavitt, J.W. 1996.Typhoid Mary: Captive to the Public's Health. Beacon Press, Boston, MA.
Bourdain, A. 2001. Typhoid Mary: An Urban Historical. Bloomsbury, New York, NY.