. According to Centers for Disease Control and Prevention, 2012), no single isolated cause is the source of an event but rather the event develops from a chain of causation, preceding events link to one another. John Snow believed that most of the people that died drank water from the Broad street pump. The preceding events however were that the people dumped fecal matter into the well, bacteria (vibrio cholerae) began to multiply, people would ingest this contaminated water, bacteria multiples in the gut leading to death (Harvard Online, 2017). John Snow was successful in establishing a cause because after his theory was tested, the epidemic stopped.
- The outbreak I chose to research was Salmonella caused by cucumbers grown by Bedner's Growers Inc., and distributed by Fresh Start Produce Sales Inc., affecting three Florida locations including Boynton Beach, Delray Beach, and West Palm Beach between April 29, 2025, and May 2025 (USFDA, 2025). This outbreak would be considered an epidemic because it was a sudden increase in the number of cases above what is normally expected in a given population (Florida) (Centers for Disease Control and Prevention, 2012). This mode of transmission is horizontal, indirect food borne mode of transmission. According to the U.S. Food & Drug Administration (2025), investigators collected an environmental sample from Bedner Growers, Inc. that was positive for Salmonella. This sample was analyzed by the Whole Genome Sequencing (WGS) and matched clinical samples from sick people infected with salmonella. This recent follow-up was in response to a 2024 Salmonella Africana and Salmonella Braenderup outbreaks linked to the same Bedner Growers (United States Food & Drug Administration, 2025). In comparison to the strategies used by John Snow, the strategies align that there was an outbreak of salmonella. 551 illnesses were recorded. Investigations showed that Salmonella Braenderup was detected in samples of canal water used at the farms that grew the cucumbers, people purchased these cucumbers and got sick.
How did John Snow use the web of causation related to cholera? Why do you believe that Snow was successful or unsuccessful in establishing a cause? Remember to cite evidence to support your position. It can be from the resources within the course.
Full Answer Section
How John Snow Used the Web of Causation (Chain of Causation):
As described in the provided text, John Snow identified a clear chain of events leading to the cholera deaths:
- People dumped fecal matter into the well. This was the initial contaminating act.
- Bacteria (Vibrio cholerae) began to multiply. This introduced the infectious agent into the water supply.
- People would ingest this contaminated water. This was the exposure pathway.
- Bacteria multiplies in the gut leading to death. This was the disease process and outcome.
Snow's genius was not just in identifying the contaminated water but in systematically mapping the distribution of cholera cases. He observed that most of the people who died had drunk water from the Broad Street pump. By plotting the cases on a map and interviewing residents, he identified a strong correlation between cholera incidence and the use of that specific water source (Harvard Online, 2017). This methodical approach allowed him to trace the "chain of causation" from the initial contamination to the final outcome.
Why John Snow Was Successful in Establishing a Cause:
John Snow was unequivocally successful in establishing a cause for the cholera outbreak. The provided text supports this assertion directly: "John Snow was successful in establishing a cause because after his theory was tested, the epidemic stopped" (Harvard Online, 2017).
His success stemmed from several key factors:
- Empirical Observation and Data Collection: Snow did not merely theorize; he meticulously collected data on cholera deaths and their connection to water sources. He went door-to-door, gathering evidence and creating a detailed map.
- Intervention Based on Theory: His theory was not just academic; it led to a direct and effective intervention. By removing the handle from the Broad Street pump, he eliminated the primary source of contaminated water.
- Immediate and Measurable Impact: The rapid cessation of the epidemic after the pump handle's removal served as compelling, real-world evidence validating his hypothesis. This direct cause-and-effect relationship between the intervention and the decline in cases strongly confirmed his understanding of the disease's transmission.
- Replicable Results: Although the text doesn't explicitly state it, Snow's work laid the foundation for understanding waterborne diseases and epidemiological investigation, demonstrating a replicable scientific method for identifying causes of outbreaks.
In essence, Snow's ability to identify the precise chain of events, implement a targeted intervention based on that understanding, and observe a swift and dramatic reduction in disease confirmed his success in establishing the cause of the cholera epidemic.
References:
Centers for Disease Control and Prevention. (2012). Principles of Epidemiology in Public Health Practice, Third Edition: An Introduction to Applied Epidemiology and Biostatistics. U.S. Department of Health and Human Services.
Sample Answer
The user's input contains a discussion of John Snow and the web of causation, as well as a description of a Salmonella outbreak linked to Bedner's Growers Inc.
The prompt then asks:
- How did John Snow use the web of causation related to cholera?
- Why do you believe that Snow was successful or unsuccessful in establishing a cause?
I will address these questions based on the information provided in the user's initial text.
John Snow's investigation into the cholera outbreak in London in 1854 is a quintessential example of applying what we now understand as the "web of causation," even before the formal theory was articulated. While the user's provided text states, "no single isolated cause is the source of an event but rather the event develops from a chain of causation, preceding events link to one another," it also describes Snow's findings in a chain-like fashion.