A Classroom Epidemic
Student Learning Objectives:
1. Determine mode of transmission for an infectious agent
2. Understand the exponential increase of infection in an epidemic situation
3. Critically analyze data to determine patient zero (initiator of epidemic)
Background:
Microorganisms which can cause human disease are called pathogens.
In order to cause disease, pathogens must be able to penetrate the first and
second lines of defense of the human immune system. Once this is achieved,
the infection and subsequent disease process can begin. Early in the infectious
state, many disease causing agents are communicable. Communicable
infectious agents can be transmitted from one person to another via direct or
indirect contact. Examples of direct contact modes of transmission are kissing,
touching, and sexual contact. Examples of indirect contact include contact with
fomites. A fomite is an inanimate object used in the transmission of an infectious
agent; for example, a doorknob or a telephone. Communicable infectious agents
can also be transmitted via water, air, or food.
Epidemiology is the study of the factors affecting the occurrence and
transmission of a disease within a community. An epidemic is a sudden
increase in the number of cases of a disease in a particular community in a given
period of time. Epidemiologists are scientists who study the when, where, why
and how of epidemics. In this exercise, students will act as epidemiologists.
Students will simulate an epidemic using a non-toxic, non-infectious, nonbiological powder as our “infectious agent.” The student will then identify infected
members of the population, mode of transmission of the infectious agent, and the
originator of the epidemic.
Materials:
Brown paper lunch bags, one per student (1 bag filled with cornstarch, the rest
filled with talc powder)
Filter paper, one piece per student
Iodine developer solution
Procedure:
1. Pick a bag from the side table. Make a note of the number on the bag.
This number is how you will be identified for this exercise.
2. Your instructor will come around and spray your right hand with water.
Shake off the excess water.
3. Reach into the bag with your moistened hand and coat it with the powder
in the bag. This is to simulate sneezing on your hand.
4. When your instructor tells you it is time, shake hands with one person
using the hand coated with the powder. Record the number of the person
you shook hands with in the first column of the data sheet (round 1).
5. When your instructor tells you it is time, shake hands with a new
person and record the number of the person in the second column of the
data sheet (round 2).
6. When your instructor tells you it is time, shake hands with a third
person and record the number of the person in the third column of the
data sheet (round 3).
7. After the third round of hand shaking, press your hand firmly to a piece of
filter paper.
8. To determine who is “infected”, spray the filter paper with the iodine
developer solution and look for a color change. A blue color means that
you are “infected”. A brown or yellow color means that you are not
infected.
9. The instructor will record all data on the overhead projector. Once all data
are collected, you will be able to determine the originator of the epidemic
or “patient zero”.
The Epidemic – Data Sheet
Person
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Round 1
Round 2
Round 3
Infected?
Who started the epidemic? _________________________
Questions for Review:
1. What was the mode of transmission for this “infectious agent”?
2. Did the numbers of the infected persons increase or decrease after three
rounds of handshaking? How many people were infected after rounds 1,
2, and 3?
3. What additional step must occur in order for our infectious agent to cause
disease in our simulated “epidemic”?
4. Provide a scenario where a fomite could be involved in the transmission of
our “infectious agent”.
5. What is the easiest and most efficient way to prevent this type of
“outbreak”?