Laboratory Activity #1: Snow on Cholera:
Observation on Cholera
1. Concerning John Barnes, what are the modes of disease transmission and what are
the epidemiologic terms by which they are identified?
Cholera was caught by John Barnes through his sick sister. Barnes caught cholera
after opening the box and handling the contaminated clothes since it had not been
cleaned. The actual transfer involved fomite transmission.
2. How long is a fortnight?
Two weeks
3. In the examples or circumstances presented, what were the various modes of
transmission stated or, at least, alluded to? Which were correct? Which were incorrect
and why? What role did personal hygiene and sanitation (including food preparation
and hand washing) play in the transmission of the disease and continuation of an
outbreak?
Person-to-person contact was the major route of transmission. A sick person's
efffluvia was also proposed as a route of transmission. Snow theorized that the
alimentary canal was the earliest site of affection. Because people were in contact
with sick persons and did not wash their hands correctly, personal hygiene and
sanitation had a role in transmission. Cholera was transferred to the stomach and
intestines when people prepared or ate meals. Cholera "evacuations" on bed
linens were also a route of transmission. Water that had been infected was
thought to be a transmitter.
4. Several instances of causal association were presented or alluded to in the examples
presented in the case. List the various instances of association that can be identified
from the examples or situations presented in the case. What role did social class,
poverty, and housing arrangements play in association? What role did water play?
Food infected by those who had cholera; water infected by feces or cholera
evacuations that was then used for cooking and drinking; involuntary passage of
evacuations from infected individuals; poverty was found to be a major risk-
factor for the spread of disease because poor people lived in cramped conditions
where cooking and eating took place in the same room as the sick person; and
lack of sanitary conditions including haemorrhagic disease.
5. Describe the disease, cholera, as presented by John Snow and also describe cholera
as it is known today.
Cholera was a sickness that was initially introduced at a sea port and
subsequently spread through human interaction, according to Snow. It might be
passed from a sick person to a healthy person via conversation. According to
Snow, a cholera agent was eaten and subsequently replicated in the stomach and
intestines. The chemical either irritated the stomach or drained fluid from the
blood flowing via the capillaries. The virus had a short incubation time and
propagated quickly. Cholera is a diarrheal disease caused by the bacteria Vibrio
