with similar characteristics, they bring it to the attention of national public
health officers. Epidemiologists collect a variety of evidence including
demographic evidence (such as geographic location, age and other defining
characteristics of victims, and mortality rate), laboratory evidence from
victims’ tissues, and evidence about environmental factors that might be
involved. Their goal is to protect public health by identifying the disease
as rapidly as possible and recommending appropriate actions to prevent
it from becoming an epidemic.
A recent example of the effectiveness of this strategy was the identification
of hantavirus pulmonary syndrome (HPS) as an emerging disease. Cases
of this apparently new disease were first recognized in May 1993. Within
four months, the infectious agent had been identified as a “new” variety of
hantavirus, the reservoir of the virus had been determined to be deer mice,
and the route of transmission (inhalation of viral particles from the rodents’
feces and urine) had been deciphered. Strategies for avoiding contact with
the virus were developed, and early diagnosis and support therapy were
recommended to reduce mortality due to the disease.
Three “mystery diseases” (unnamed for the students, but based on HPS,
Lyme disease, and Lassa fever) are the initial focus of this lesson. HPS
was first recognized in 1993; Lyme disease first came to the attention of
public health workers in 1975 as an unusual number of cases of juvenile
rheumatoid arthritis in children in Lyme, Connecticut; and Lassa fever
was first identified in an outbreak in Nigeria in 1969. Cases of HPS were
originally clustered in the Four Corners region of the U.S. Southwest, and
the majority of cases to date have been found there. Lyme disease is the
most commonly diagnosed tick-borne disease in the United States, with the
majority of cases clustering in the Northeast, although cases have occurred
in 48 of the 50 states. Lassa fever outbreaks occur in West Africa.
Investigating these diseases leads students to recognize that all three of
them “emerged” as a result of environmental changes and/or movement of
humans into areas inhabited by the organism that serves as a reservoir for
the pathogen. Lesson 3, Superbugs: An Evolving Concern, and Lesson 4,
Protecting the Herd, help students understand two factors involved in the
re-emergence of infectious diseases.
62
Photocopies and Transparencies
Equipment and Materials
In Advance
• 1 copy for each student of
• 1 overhead projector
Masters 2.1 and 2.11
• blank transparencies
• 1 copy for each group of
• (Optional) Computers with
Masters 2.2, 2.3, 2.4, 2.5, 2.6,
access to the Internet
2.7, 2.8
• 1 copy for half the groups of
Master 2.9
• 1 copy for the other half of
groups of Master 2.10
• 1 transparency of Master 2.11
Preparation
Make the investigation files: copy Masters 2.2, 2.3, and 2.4 and assemble
them into file folders that you label “Physician’s File,” “Laboratory Scientist’s
File,” and “Field Researcher’s File.” You may want to use a different-colored
folder for each type of file. Make enough sets of these files so that no more
than three or four students (one student from each of three or four different
groups) study the documents in the file together. For example, for a class of
30 students (10 groups), prepare three sets of each type of file.
1. Introduce the lesson by asking students to suppose that a friend
Procedure
developed a strange rash and then a fever accompanied by severe
vomiting and diarrhea. Their friend was hospitalized for a week before
finally recovering. Then, they hear about a student in another class
who had similar symptoms, and they learn that this student’s cousin
was also sick with fever, vomiting, and diarrhea. A few days later, they
hear a television report about a strange illness affecting five students
at a nearby high school. The symptoms described sound just like
those experienced by their friend. Ask students to suggest questions
they might ask about how to protect themselves from this illness.
Write these questions on the board or a transparency.
If students ask, explain that the symptoms do not indicate a particular
disease but are used to get students thinking. Complete this step
quickly, accepting and listing four or five reasonable questions from
students, such as, “Do all the sick people have the same disease?”
“What is the cause of the disease?” and “Do the victims have anything
in common that can tell us how the disease is transmitted?” It is
important to leave these questions on the board or the overhead
projector so that students can refer to them as they complete
the lesson.
63
Student Lesson 2
Emerging and Re-emerging Infectious Diseases
2. Tell students that public health officers are responsible for answering
these types of questions when a cluster of unusual cases of disease
occurs. Explain that in this lesson, students will follow in the
footsteps of public health officers to answer some of the questions
they listed about a mystery disease. Give a copy of Master 2.1,
Three Mysterious Diseases, to each student, and ask four volunteers
to read the script to the class.
If you have students who are interested and talented in drama, you may
want to give them the scripts the previous day and ask them to read
them dramatically to the class.
If students ask what you mean by “unusual cases of disease,” explain that
it could mean a variety of unexpected occurrences including symptoms
that are rare in general, symptoms that are rare in the population in which
they are now occurring, or unusual severity of illness or fatality rates.
If you can project the video for the whole class, you can use
the “Three Mysterious Diseases” videos on the Web site to
introduce the lesson. Go to http://science.education.nih.gov/
supplements/diseases, and click on “Web Portion of Student Activities” and then “Lesson 2—Three Mysterious Diseases.”
3. Group students into teams of three and tell them they will spend the
next 30 minutes investigating the first mystery disease. Ask them
to assign each group member one of the following roles: physician,
laboratory scientist, or field researcher. Explain that each of these
experts will look for clues that will help each group answer the
questions the class listed in Step 1.
We suggest that you use the same groups as in Lesson 1.
4. Identify a station in the room for each of the three experts. Place
copies of the relevant master (Masters 2.2, 2.3, or 2.4) at each station.
Give each group one copy of Master 2.5, Notes from the Physician’s
Investigation; Master 2.6, Notes from the Laboratory Scientist’s
Investigation; and Master 2.7, Notes from the Field Researcher’s
Investigation. Direct students to go to the appropriate station and
review and discuss the clues they find there about the disease with
their colleague “experts” from the other groups. Ask them to record
significant information on the forms you distributed. Tell students
they will have 15 to 20 minutes to complete their research.
Move among the groups during this time, answering their questions and
using probing questions to direct their attention to significant details in
their information. Students in the field researcher groups may wonder
why there is no interview transcript from “J. McDonald.” Draw their
attention to the “Other Comments” on McDonald’s “Investigation of
Victim’s Home” report, in which she indicates that the victim’s mother
and aunt refused to be interviewed.
64
Tip from the field test: To save time and reduce confusion, place three
or four copies of Masters 2.5, 2.6, and 2.7 at the appropriate stations
before class. Then tell students they will find a copy of the form they
need to complete at the station.
5. Reconvene the original groups and give one copy of Master 2.8,
Mystery Disease 1 Final Report, to each student. Allow group members
10 minutes to pool their information and complete the report form.
Again, move among the groups, answering their questions and directing Collect students’ Final their attention to significant details. Students may have particular
Reports and review them
difficulty with the final task, which asks whether the disease is
to evaluate how well
emerging, re-emerging, or endemic. Help them come to the conclusion
students were able to
that this is an emerging disease by asking questions such as, “Was there
evidence that this disease is common in the Southwest?” “Was there
identify the evidence that
evidence that it was not one of these common diseases?” “What did you
supported or refuted a
decide was the cause of the disease?” “Has this infectious agent been
claim about the disease.
known to cause a disease with the ARDS symptoms?” and “What is the
Identify areas where
evidence that this is an ‘old’ disease? . . . that it is a ‘new’ disease?”
students could improve
and discuss them with the
6. Distribute Master 2.9, Mystery Disease 2 Final Report, to half the
class when you return
groups and Master 2.10, Mystery Disease 3 Final Report, to the
remaining half. Explain to students that a group of experts similar
their papers.
to those in their groups pooled information from their investigations
to complete these reports. Ask students to study the report forms
while you distribute one copy of Master 2.11, Mystery Diseases
Summary Table, to each student.
7. Direct students to complete the table on Master 2.11 for the two diseases
for which they have report forms.
8. Display a transparency made from Master 2.11, and ask several groups to report one piece of information as you complete the first row of
the table. Ask the remaining groups whether they have additional
information and whether they disagree with any of the information
provided by the other groups. Follow the same procedure for the
other two mystery diseases.
All three diseases are classified as emerging diseases and although
students are not given this information, all three have probably
occurred for hundreds if not thousands of years. Nevertheless, only
recently have cases occurred in sufficient numbers that they were
recognized as specific diseases. The infectious agents for the three
diseases are transmitted by
• Mystery Disease 1—contact with deer mouse ( Peromyscus
maniculatus) urine and feces
• Mystery Disease 2—bite from deer ticks ( Ixodes dammini)
• Mystery Disease 3—contact with rat ( Mastomys natalensis) urine
and feces, and close contact with victims of the disease
65
Student Lesson 2
Emerging and Re-emerging Infectious Diseases
The environmental factors involved are
• Mystery Disease 1—climatic conditions favoring large deer mice
populations and human encroachment into areas inhabited by
This is a good time to note
deer mice
how technological advances
• Mystery Disease 2—climatic conditions favoring large acorn
harvests and human movement into wooded areas
have improved our ability
• Mystery Disease 3—conditions that reduce competition from
to identify the infectious
R. rattus, including human efforts to reduce the R. rattus population
agents for mysterious
diseases. Identification
9. Allow students to examine the summary table and then ask them to
of the spirochete type of
list any common features they note about the three mystery diseases.
bacterium as the cause
Lead a class discussion by asking, “Can you see one overall factor that
resulted in the emergence of all three of these diseases?” and “What
of Lyme disease required
does this suggest about things people need to consider as we develop
nearly seven years, whereas
land for residential and business purposes?”
molecular biology
techniques available in
Common features of the three mystery diseases, as revealed on Master
1993 meant that the
2.11, are that all the diseases are emerging, the transmission of the
infectious agent for HPS
infectious agent involves a nonhuman animal, and environmental
was identified within a
factors strongly help explain their occurrence. Guide students to the
understanding that environmental and ecological factors, combined
month. Continuing
with the movement of humans into previously uninhabited areas, help
NIAID-supported research
explain the relatively sudden appearance of these “new” diseases.
on the Lyme disease
spirochete has led to
You may want to reveal the names of the three mystery diseases at
improved diagnosis
this time:
of the disease and the
• Mystery Disease 1—hantavirus pulmonary syndrome (HPS)
development of a new
• Mystery Disease 2—Lyme disease
vaccine to prevent it.
• Mystery Disease 3—Lassa fever
Explain to students that these diseases were first recognized in 1993
(HPS), 1975 (Lyme disease), and 1969 (Lassa fever). Although the
symptoms and “clues” presented in the mystery disease cases would
immediately implicate HPS, Lyme disease, or Lassa fever if physicians
saw them today, in 1993, 1975, or 1969, these three diseases were “new”
to healthcare workers, just as they were to students in this lesson.
10. Ask students to complete individually, in writing, the sentences at
the bottom of Master 2.11,
In Step 10, students are
Mystery Diseases Summary Table.
challenged to synthesize
11. Collect students’ assignments from Step 10 and close the lesson by
in their own words the
noting several responses (anonymously) and engaging the students
discussion from Step 9.
in a discussion of the issues that should be considered to avoid or
Completing the sentences
minimize the risks of emerging diseases.
requires them to state and
elaborate on the lesson’s
Completing the lesson should lead students to recognize that changing
environmental conditions create opportunities for new or previously
major concept.
rare diseases to affect large numbers of people. Students are likely
66
to respond to the second question by a blanket statement such as,
“People should stay out of uninhabited areas.” Challenge them to think
more deeply by asking questions such as, “Should you or anyone else
be allowed to tell people where they can live?” “What if people in a
developing country have an opportunity to dramatically increase their
income, as well as their country’s productivity, by developing an area
previously uninhabited by people? Do the advantages of economic
development outweigh the risks of emerging diseases? What do you
need to consider to make this evaluation?” and “How might medical
and ecological research efforts help resolve these dilemmas?”
You may want to give students the example of the Aswan Dam in Egypt.
Schistosomiasis is a disease that causes diarrhea, abdominal pain,
and liver problems. Chronic infections may lead to liver failure and
may also affect the central nervous system. The disease is caused by a
helminth that has a complex life cycle, including stages in both snails
and the human bloodstream. Because snails thrive in still waters such
as those found in irrigation canals and artificial lakes, the incidence of
schistosomiasis frequently increases following construction of dams.
Although this was known before the Aswan Dam was built, the officials
involved in the decision felt that the economic advantages of the dam
outweighed the disease consequences. Before the dam was built, about
1 percent of the schoolchildren in the area had schistosomiasis. After
the dam was built, the incidence of schistosomiasis among children in
some villages near the artificial lake rose to 100 percent. Since then,
Egypt has spent part of the profits from the Aswan Dam on a major,
ongoing chemotherapy campaign against schistosomiasis.
This example also shows that the incidence of “old” diseases may be
affected by environmental changes. Schistosomiasis is not a “new”
disease, but the increased incidence of the disease makes it a candidate
for a re-emerging disease. Other factors related to disease re-emergence
are explored in the next two lessons.
Several popular books on emerging infectious diseases make exciting
Potential
reading and provide further illustration of scientists’ work in identifying
and limiting the risks of emerging diseases. Assign students to read and
Extensions
report on books such as The Hot Zone, by Richard Preston (which describes
outbreaks of Ebola hemorrhagic fever), The Coming Plague, by Laurie Garrett
(which describes the efforts of scientists and policymakers regarding
a variety of emerging and re-emerging diseases, including HPS, Lassa
fever, malaria, and Legionnaire’s disease), and Restless Tide: The Persistent
Challenge of the Microbial World, by Richard M. Krause.
67
Student Lesson 2
Emerging and Re-emerging Infectious Diseases
Lesson 2 Organizer
What the Teacher Does
Procedure
Reference
Ask students to imagine the scenario in Step 1 on page 63. Ask
Page 63
students to suggest questions they might ask about how to protect
Step 1
themselves from the illness. Write students’ questions on the board.
For classes with Internet access, Step 2
Page 64
Show the Three Mysterious Diseases video clips from the Web site.
Step 2
(Students may still appreciate having the copy of Master 2.1
for reference.)
For classes without Internet access, Step 2
Page 64
Tell students that public health officers answer these types of
Step 2
questions when a cluster of unusual cases of disease occurs. Explain
that students will play the role of a public health officer to answer
the questions they have about a mystery disease. Give each student
a copy of Master 2.1. Ask for volunteers to read the script aloud to
the class.
Group students into teams of three. Ask groups to assign a role to
Page 64
each student. Allow 30 minutes for groups to investigate the first
Step 3
mystery disease. Experts should look for clues to help answer the
questions from Step 1.
Place copies of Masters 2.2, 2.3, or 2.4 at three stations (Physician’s
Page 64
File, Laboratory Scientist’s File, or Field Researcher’s File).
Step 4
Ask students from the original groups to meet with the same
experts from the other groups at the appropriate station. Allow
15 to 20 minutes for these new groups to review information in
their files and discuss the clues about the disease. Ask groups to
record significant information on a copy of the master appropriate
for their expert role (Master 2.5, 2.6, or 2.7).
Ask the “experts” to return to their original groups. Give each
Page 65
student a copy of Master 2.8. Allow 10 minutes for group members
Step 5
to pool their information and complete the report.
Give Master 2.9 to half the groups and Master 2.10 to the other
Page 65
half. Ask students to study the report forms.
Step 6
68
What the Teacher Does
Procedure
Reference
Give each student a copy of Master 2.11. Ask students to complete
Page 65
the table for the two diseases for which they have report forms.
Steps 6
and 7
Display a transparency of Master 2.11. Ask several groups to report
Page 65
one piece of information to complete the first row of the table.
Step 8
Ask other groups if they have other information or disagree with
any information provided by other groups. Complete the table
using this approach.
Discuss the summary table with students by asking the following
Page 66
questions:
Step 9
• Are there any common features you can list about the three
mystery diseases? What are they?
• Can you see one overall factor that resulted in the emergence
of all three of these diseases?
• What does