Define the following terms: epidemiology, epidemic, reservoir, and
three methods of transmission.
the source of a simulated epidemic.
every infectious disease, the disease-producing microorganism, the pathogen,
must come in contact with the host, the organism that harbors the
pathogen. Communicable diseases can be spread either directly or
indirectly from one host to another. Some microorganisms cause disease
only if the body is weakened or if a predisposing event such as a wound
allows them to enter the body. Such diseases are called noncommunicable
diseases; that is, they cannot be transmitted from one host to another.
The science that deals with when and where diseases occur and how they
are transmitted in the human population is called epidemiology. Sporadic
diseases are those that occur occasionally in a population; an example
is polio. Endemic diseases such as pneumonia are constantly present
in the population. When many people in a given area acquire the disease
in a relatively short period of time, it is referred to as an epidemic
disease. Influenza often achieves epidemic status.
can be transmitted by direct contact between hosts. Droplet
infection, when microorganisms are carried on liquid drops from a
cough or sneeze, is a method of direct contact. Diseases can also be transmitted
by contact with contaminated inanimate objects, or fomites. Drinking
glasses, bedding, and towels are examples of fomites that can be contaminated
with pathogens from feces, sputum, or pus.
diseases are transmitted from one host to another by vectors. Vectors
are insects and other arthropods that carry pathogens. In mechanical
transmission, insects carry a pathogen on their feet and may transfer
the pathogen to a persons food. For example, houseflies may transmit
typhoid fever from the feces of an infected person to food. Transmission
of a disease by an arthropods bite is called biological transmission.
An arthropod ingests a pathogen while biting an infected host and
then transfers the pathogen to a healthy person in its feces or saliva.
The continual source of an infection is called the reservoir. Humans
who harbor pathogens but who do not exhibit any signs of disease are called
epidemiologist compiles data on the incidence of a disease and
its method of transmission and tries to locate the source of infection
in order to decrease the incidence.
Unknown1, Swab, Paper
1One swab is inoculated with GloGerm
powder. Glo powder fluoresces under ultraviolet (UV) light.
- Work in groups
of 6 to 10 students.
- Divide the recording
paper into six sectors labeled "1" to "5." Carefully
read steps 2-4 before proceeding.
- Put the glove on
your left hand. Holding the swab, dip the cotton in your unknown powder
rub the powder on the palm of your left hand (i.e., on the glove). Gently
shake off loose powder and reapply. Rub the powder over your entire
- Shake left hands
with a classmate when the instructor gives the signal. Shake hands so
your fingers touch the other's palm and vice versa. After shaking hands,
touch your fingers to the first sector of the paper. Record the person's
name and swab number.
- Repeat step 3,
shaking hands with four other classmates. Remember to touch your fingers
to the corresponding sector of the paper after each handshake. Keep
- Examine your paper
under a UV light and record your results in your Lab Report.
Do not look at the ultraviolet light and do not leave your hand exposed
What was the purpose
of this experiment?
had the "disease?"
2. Diagram the
path of the epidemic in your group.
1. Could you
be the "infected" person and not have glo powder on your paper? Explain.
2. Do all people
who contact an infected individual acquire the disease? Explain.
3. When does
an epidemic stop?
4. What was the
method of transmission of the "disease" in this experiment?