Field Epidemiology Essay
1. Hypothesis generation is a preliminary step in conducting an outbreak investigation. It is the process of gathering information about ill persons, about all of their potential exposures, and about the circumstances that gave rise to the outbreak. Did John Snow illustrate the modern-day idea of hypothesis generation? Why or why not?yes. he became aware of what was going on and linked the findings to the broad street pump. 2. In the 1850’s, the germ theory of disease did not yet exist.
Yet John Snow illustrated one of the modern tenets of infectious disease transmission. He suspected that ‘organic matter’ had to be present in water that someone ingested in order to cause illness. How was this early form of the germ theory was illustrated? in the 1850’s, miasma was the way scientist thought a pathogen can enter the host. John snow did a series of chemical and microscope examinations on the water from the broad street pump and the findings was able to get the pump disabled. He also noticed that all deaths occurred by the broad street pump which later was proven that there had been a cholera outbreak in that part of town.
3. One key way of gathering information in field epidemiology is conducting interviews. What information did John Snow gather through interviews, that he could not have obtained any other way? john snow went around to families of deceased persons to collect information on where they got their water from and it all connected back to the broad street pump. 4. For most diseases, there is an expected rate of disease in the community. For example, several cases of fever and chills during flu season might be expected at a primary school. This expected level of disease is often called the background rate.
When the rate of disease exceeds the background rate, an outbreak may be occurring. Which of the following scenarios from Episode II represents the background rate of cholera, according to John Snow? a) “The other two deaths, beyond the district which this pump supplies, represent only the amount of mortality from cholera that was occurring before the irruption took place.” b) “There were sixty-one instances in which I was informed that the deceased persons used to drink the pump-water from Broad Street, either constantly or occasionally.” c) “In three other cases, the deceased were children who went to school near the pump in Broad Street. Two of them were known to drink the water; and the parents of the third think it probable that it did so. ” d) “In five of these cases the families of the deceased persons informed me that they always sent to the pump in Broad Street.”
5. A disease attack rate is the number of new cases of a disease per population at risk. This is often expressed as a percentage, i.e. the number of people with disease divided by the number of people in the population. What was the attack rate for those 89 cholera deaths that Snow obtained information about from the General Register Office?
6. Today, the removal of the Broad Street pump-handle is a legendary action taken to curtail a deadly outbreak. However, this action was taken as the result of another crucial aspect of nearly all field epidemiology investigations today. The important aspect of John Snow’s actions was not the actual removal of the pump handle; it was a more basic step of every field epidemiology investigation. What did he do? he communicated with other people in the field and shared his information with people who were concerned and with people with who he can help.
7. In the narrative, John Snow states that by the time the pump-handle was removed, “There is no doubt that the mortality was much diminished… by the flight of the population… [But] the attacks had so far diminished before the use of the water was stopped, that it is impossible to decide whether the well still contained the cholera poison in an active state, or whether, from some cause, the water had become free from it.” Thus, he is uncertain whether preventing use of the Broad Street pump had any effect on limiting cholera cases. Often, by the time investigation is conducted and source of the outbreak is localized, incidence of disease is decreasing naturally. In this case, should you even invest the time, money, and resources to investigate the outbreak? Why or why not? Yes because you can always find more than what you expected. You can find out a lot more about the pathogen at hand like how it produces or where its found and this information can help you stop it.