Activity
Major
Project Connection:
In
the first 15+ minutes of class, students will meet in their
Public Health issue groups
to work through their “Get
the message out” sheets. Pass out the “Get
the message out” detailed sheets and go over the
project the students will be doing with their groups. It
might be useful to have the students be the ones to read
the handout. They will be expected to identify their topic,
their audience, why they chose that audience, and then
assign tasks to get the poster research done. Each member
of the group will have an assigned task, and as a group
they will decide on a timeline to get things done. You
will collect the sheets at the end of class, students should
have a copy of their tasks for completion.
1. Introduce the module and this activity
by asking students, “What disease do you think is the
greatest threat to students in this class? What disease
do you think is the greatest threat to the world’s
population?” Solicit several responses and
entertain a brief discussion about the diseases students
perceive as threats and why. List students’ responses
on the board or a transparency.
Heart disease was the top killer globally in 1998.
AIDS and cancer are likely to be two of the top threats
students perceive. According to the World Health
Organization (WHO), in 1998 AIDS was the fourth highest
killer worldwide, while cancer of the trachea, bronchus,
or lung was the ninth highest killer. Also in the
top 10 killers globally were cerebrovascular disease
(second), pneumonia (third), chronic obstructive
pulmonary disease (fifth), diarrheal diseases such
as cholera (sixth), perinatal conditions (seventh),
tuberculosis (eighth), and traffic accidents (10th).
2. Tell students that, as a class, they will take
a quiz on some past and current causes of death and
illness. Explain that you do not expect them to know
the answers to these questions, but ask them to make
well-reasoned guesses based on what they do know.
Then, display a transparency of Master 1.1, Causes
of Death Quiz, solicit students’ answers to
each item, and provide the correct answers.
(If you have sent away for the BSCS free curriculum
supplement and have the equipment to project the
video Infectious Disease Then and Now on the CD-ROM
for the whole class, you can substitute this video
for the quiz. Follow the instructions on page 31
to load the CDROM into the computer you will use.
The video covers roughly the same content and may
take less time than the quiz. )
3. Explain that the quiz emphasized the impact of
infectious diseases on people’s health and
well-being. Point out that even though medical advances
in the last century have resulted in far fewer deaths
from infectious diseases than at any other time in
history, those diseases are still the leading cause
of death worldwide and the third leading cause of
death in the United States. Explain that in this
activity they will learn about some infectious diseases
that cause problems in the world today.
You may need to distinguish infectious
diseases from noninfectious diseases. Ask students
to review
the
Causes of Death Quiz and identify some of the infectious
and noninfectious diseases listed there. If necessary,
point out that noninfectious diseases such as cancer,
heart disease, and cystic fibrosis cannot be “caught,” and
that infectious diseases such as AIDS and tuberculosis
are caused by living (or quasi-living, in the case
of viruses and prions) agents that can be transmitted
from one individual to another.
Identifying
a disease as “infectious” or “noninfectious” has
recently become more complex than it used to be. Researchers
have discovered that infectious agents may play a role
in some diseases that were previously considered noninfectious,
chronic conditions. For example, there is evidence that
gastric ulcers are caused by Helicobacter pylori bacteria.
Similarly, infection by Chlamydia pneumoniae may contribute
to the development of cardiovascular disease, leading some
people to question whether heart disease might be infectious.
4. Organize students in teams of three and distribute five
Disease Cards made from Master 1.2 to each team. Distribute
the cards in such a way that each disease is reviewed by
at least one team.
5. Explain that scientists find it useful to group diseases
in different ways, depending on the problems they want
to address. Direct the teams to review their disease cards
and sort them into piles that represent different categories
of infectious agents.
An important science process skill is identifying commonalities
and differences and devising classification systems. In
this step, students have the opportunity to practice this
skill, and in later steps they consider the usefulness
of classifying diseases in various ways.
6. Solicit headings for the categories identified from
several teams and write them on the appropriate place on
Disease Classifications. Then, ask the other teams to name
one or more diseases they classified in the categories
and write these into the appropriate columns. Ask students
to describe the symptoms of each disease as they do so.
7. Ask students to suggest reasons why scientists might
find it useful to classify diseases based on the type of
infectious agent.
If students need help with this, ask them to review the
treatment for each of the diseases within a category and
the evidence (symptoms) that occur in each. Students should
notice that diseases caused by the same type of infectious
agent tend to have similar types of treatment strategies,
and that similar symptoms occur in diseases caused by different
types of agents. It is useful to classify diseases by the
type of infectious agent because that indicates the type
of treatment that may be more effective than merely a review
of symptoms.
8. Next, ask students to re-sort their disease cards based
on the mechanism of transmission for each disease.
9. Repeat Steps 6 and 7 for this criterion.
It is useful to classify diseases by the way they are transmitted
because a disease’s mode of transmission may suggest
an effective preventive measure. For example, the spread
of diseases such as AIDS and Ebola hemorrhagic fever that
are transmitted by intimate contact can be stopped or reduced
through education and elimination of some behaviors (such
as burial practices in which family members disembowel
the deceased in non-sterile conditions) and institution
of other behaviors (such as proper disease control measures
in hospitals). The spread of vector-borne diseases such
as malaria can be prevented by measures that reduce the
size of the vector population or that limit contact between
humans and the vector.
10. Finally, have students re-sort their cards based upon
the history of the occurrence of the disease. Then, repeat
Steps 6 and 7.
Students likely will identify two categories: “new” (for
example, AIDS, Ebola, and Legionnaire disease) and “old” (for
example, strep throat, guinea worm disease, pneumonia,
polio, and tuberculosis). If this is the case, fill these
headings into the first two columns on Disease Classifications
and list the diseases named by students. Then challenge
them to re-examine the “old” diseases they
listed and to subdivide that category. Assist them by asking
a question such as, “Is there any difference in the
history of the ‘old’ disease tuberculosis and
the ‘old’ disease pneumonia?” When students
make the appropriate distinction, add the new headings
for the second and third columns on Disease Classifications
and re-list the diseases accordingly. Students should note
that whereas all of the old diseases are described as “present
from antiquity,” the incidence of some of them has
increased recently (in particular, the incidence of some
has increased recently after declining in the past). The
two categories from the subdivided “old” category
could be renamed “Old and Increasing” and “Old
and Remaining Constant.”
11. Supply the headings “Emerging” for the
apparently new diseases, “Re-emerging” for
diseases that have recently increased in incidence after
a decline and “Endemic” for diseases that have
remained relatively constant in incidence. Write these
labels at the heads of the appropriate columns.
The disease cards provide examples of all three types of
diseases, as shown in Figure 17.
Both polio and guinea worm disease are diseases that have
declined dramatically and, hopefully, are on their way
to global eradication. Cholera and influenza are more complicated
examples that are less easily classified. Based on the
information on their cards, students will likely classify
cholera as a re-emerging disease and influenza as an endemic
disease. Depending on the sophistication of your students
and the time available, you may simply accept their initial
categorization or you may choose to share the additional
information below and ask them where they would categorize
these two diseases. In either case, note that the categorization
of infectious diseases into these three areas is somewhat
subjective, and different researchers may categorize them
differently based on the weight they give to various characteristics.
Cholera may be classified as either re-emerging because
of increasing incidence due to the spread of the disease
in Africa, or emerging because of the appearance of the
new strain Vibrio cholerae 0139. This strain combines the
greater virulence of the classic V. cholerae strain with
the long-term survivability of the V. cholerae strain called
El Tor. Influenza is probably most accurately classified
as an emerging disease because, although the flu occurs
every year, each strain of the influenza virus is genetically
distinct. In this sense, it is a constantly emerging pathogen.
You may also want to elaborate on the definition of emerging
diseases by noting that this category includes (1) diseases
that are truly “new” among humans (few, if
any, examples fall into this subcategory); (2) diseases
that probably affected a few individuals hundreds or thousands
of years ago, but have just recently affected enough of
the population that they are noticed (AIDS and Ebola hemorrhagic
fever are examples for this subcategory); and (3) diseases
that affected people hundreds and thousands of years ago,
but have just recently been recognized as due to an infectious
pathogen (gastric ulcers caused by Helicobacter pylori
is an example that falls into this subcategory). Many researchers
include re-emerging diseases as a subcategory of emerging
diseases.
Figure
17 History of Occurrence
Emerging
Diseases
AIDS, cholera, CJD,
Ebola hemorrhagic fever,
influenza, Legionnaire
disease, Lyme disease
|
Re-emerging
Diseases
tuberculosis, malaria,
schistosomiasis
|
Endemic
Diseases
pneumonia, polio, guinea
worm disease, plague,
strep throat
|
Closure
Conclude the activity by telling students that public
health workers are becoming increasingly concerned about
the emergence of “new” diseases and the re-emergence
of some “old” diseases. These biologists have
found it useful to classify infectious diseases as emerging,
re-emerging, or endemic because there tends to be different
factors related to each category. Given what they have
covered in History class what do they think about the impact
of emerging and re-emerging diseases today as compared
with those in the past? Tell students that they will explore
factors related to disease emergence and re-emergence in
upcoming activities.
Homework
In
their science notebooks, have students write a reflective
conclusion.
Students should define in their own words what
an emerging disease is and what a re-emerging disease is.
What did they learn? What new questions do they have? How
does the lab connect to “real life?”
-OR-
Internet Web sites maintained by both the Centers for Disease
Control and prevention (www.cdc.gov/)
and the World Health Organization (www.who.org/)
include health topic sections that provide information
on infectious (and noninfectious)
diseases. Assign students to use these and other resources
to create additional disease cards and to classify those
diseases as emerging, re-emerging, or endemic. |
Embedded
Assessment
Are
students able to recognize that infectious diseases are
a continuing problem among all human populations?
Can
they define and give examples of emerging and re-emerging
infectious diseases?
|
