to think back to the diseases that they have been
introduced to over the past few weeks (if you are
doing this lesson out of order ask students to identify
some diseases that are of interest.) How are these
diseases spread from person to person? Have students
list the diseases on index cards. During this time,
discuss the difference between an infection, the
action of a disease-causing pathogen entering the
body, and a disease, when the body is not able to
immediately fend off the pathogen and the pathogen
is able to cause damage to the body.
2. Reviewing the diseases that students named can
they identify what type of pathogen has caused the
disease? Is this a virus, a bacterium, fungi, protozoa,
or a parasitic worm? Previously students have been
briefly introduced to different types of pathogens;
this is an opportunity to revisit the classifications
of these pathogens. Concentrate on making sure students
note that not all microorganisms are of the same
type and that they know the difference between a
virus and bacteria.
Viruses consist of a small amount of nucleic acid
(DNA or RNA) enveloped by a protective coat of protein,
or protein and lipid. Viruses are smaller than a
cell and only reproduce by invading eukaryotic cells
and then making use of the invaded cells’ reproductive
structures which viruses lack. Viruses are not considered
to be living. Viruses are considered obligate intracellular
parasites. (Particles of a similar type that invade
prokaryotes are known as bacteriophages.) Examples
of diseases caused by a virus infection include the
common cold, smallpox and HIV/AIDS.
bacteria are considered living organisms. Prokaryotic
cells and bacteria are typically unicellular and
don’t have the membrane bound organelles that
are found in eukaryotic cells. Bacteria are able
to reproduce asexually through binary fission.
3. If students are able to identify the type of pathogen
associated with a disease they should note that on
the disease index card. Review the different diseases
and pathogens as a class. Are some more virulent
than others? Do some diseases seem to pass through
a population more quickly than others? As a class
make a chart (see Overhead # 1) that includes the
disease’s name and whether it has a pathogen
or non-pathogenic cause. If pathogenic, what type
of pathogen causes the disease, is it a virus, a
bacteria, a fungi, or a parasitic worm? How is it
passed from one host to another? Use the Teacher
Guide #1 to help students provide examples of a variety
of pathogenic and non-pathogenic causes.
4. Student groups are each given a disease caused
by a pathogen (human or veterinary) and asked to
answer a number of questions. Students should be
encouraged to provide graphical as well as written
responses to some of these questions:
i. What cell type? What pathogen type?
ii. How does it invade the host? What is its’ host?
iii. What is the immune response to it? Are there
any natural, evolutionary responses to it (i.e.
with malaria and sickle cell anemia?)
iv. Where is it when it is outside of the organism
(if it ever is)? (Describe its’ life cycle)
v. How is it passed from one host to another?
vi. Are there artificial means that have been used
to combat this?
vii. Will antibiotics or vaccinations work with
this disease why? Why not?
viii. What are the ramifications of infection/invasion?
ix. Does it affect all people equally?
5. Students should present their information to
class and fill in a class table addressing these
6. Review the class table. Are there patterns
that you can see among viruses, bacteria, fungi
In how they infect and cause disease? As a class,
up with a summary for each type of pathogen.
How does the structure of the pathogen play a
in the infection and in the disease?
Students will need to spend some time researching their
disease, answering the questions and preparing to present
it to the class.
Homework - Major Project
Remind students that the Public Health Reflection II Homework
sheet is to be turned in at the start of class tomorrow,
before beginning the “Describe the perfect pathogen” lesson.
Class discussion and the charts allow for assessment
of students’ ability to define a pathogen versus
non-pathogen cause to a disease.
2. Student presentation and subsequent chart allows for
assessment of the ability to identify four different
types of pathogens.
3. Student summary provides an opportunity for assessment
of students to articulate any commonalities/patterns
between diseases and infections of a specific type of