Deadly Disease among Us

From: Emerging and Re-emerging Infectious Diseases by Joseph D. McInerney and Lynda B. Micikus. Written under a contract from the National Institutes of Health and National Institute of Allergy and Infectious Diseases (NIH Publication No 99-4645) 1999. This unit is available free of charge to teachers via http://www.bscs.org

Minor modifications by: Kirstin Bittel

Time: 1 class period
Preparation Time: 15 minutes making copies of Quiz and Disease Cards.
Materials: You will need to prepare the following materials before conducting this activity:

This activity engages students in the seriousness of infectious diseases by making them aware of the widespread impact of such diseases. Students discover that some diseases are relatively new to humankind (emerging diseases); while others that had been nearly eliminated in developed countries are now beginning to increase in incidence (re-emerging diseases). They also learn that many diseases have been a perennial problem in human populations, never significantly declining (endemic diseases).
Students complete a short “surprising statistics” quiz on the impact of infectious diseases, then classify several diseases as “emerging,” “re-emerging,” or “endemic.”

This activity introduces emerging and re-emerging infectious diseases as a public health issue that can be examined using scientific methods (for example, collecting and organizing data into categories).

Students will be able:
1. Recognize that infectious diseases are a continuing problem among all human populations.
2. Define and give examples of emerging infectious diseases.
3. Define and give examples of re-emerging infectious diseases.

National Science Education Standard:
Standard F: Personal and Community Health
Students should develop an understanding of
-- personal and community health
-- natural and human-induced hazards
Standard G: History and Nature of Science
Students should develop understanding of
-- historical perspectives

Teacher Background
In developing countries, where much of the population lives in conditions of extreme poverty, infectious diseases remain the leading cause of death. In the United States, prevention and control of infectious diseases have been so successful in the past half century that many people view infectious diseases as either a thing of the past or minor illnesses easily treated and cured, except among the very young, very old, or seriously ill.

In recent years, however, Americans have been shocked by the emergence of a variety of “new” infectious diseases. For example, Escherichia coli strain 0157:H7 caused severe vomiting and diarrhea among patrons of Jack in the Box restaurants in Washington State in 1993 and among children swimming in public pools in Atlanta, Georgia, in 1998. A previously unrecognized virus (a hanta virus) caused a frequently fatal respiratory illness among apparently healthy young people in the Southwest. New diseases have emerged in developing countries as well. Ebola hemorrhagic fever, which was first described in 1976 in Zaire (now the Democratic Republic of the Congo), has particularly horrifying symptoms and a fatality rate of 50 to 90 percent. And AIDS, which emerged simultaneously in the United States and Africa in the early 1980s, has become a global pandemic. Likewise, many diseases thought to be adequately controlled appear to be making a “comeback.” In developed countries, public health measures such as sanitation, sewage treatments, vaccination programs, and access to good medical care, including a wide range of antibiotics, have virtually eliminated “traditional” diseases such as diphtheria, whooping cough, and tuberculosis.

However, many of these diseases are becoming a public health problem once again, as immunization programs and other public health standards are enforced less vigorously and, especially, as antibiotic-resistant pathogens evolve. In fact, medical workers have identified strains of pneumonia-causing Staphylococcus aureus that are resistant to all of the currently available drug treatments; physicians and public health workers are also concerned that we are about to re-enter the pre-antibiotic era for treating such diseases. Among the diseases “re-emerging” as a consequence of microbial resistance are tuberculosis and malaria, the two leading causes of death from infectious diseases worldwide.

Prerequisite Student Knowledge
Before beginning this lesson, students should be familiar with bacteria and viruses and understand that infectious diseases are due to infection of the body by an external agent.

Pre-Lab Preparations
You will need to prepare the following materials before conducting this activity:

  • Master 1.1, Causes of Death Quiz (make 1 transparency)
  • Master 1.2, Disease Cards (make a classroom set)
    To make the disease cards, copy Master 1.2 and cut the copy apart to form individual cards. Glue each card to a 5 × 7 index card.
  • Master 1.3, Disease Classifications (make 1 transparency)
  • Red transparency pen




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,

Endemic Diseases
pneumonia, polio, guinea
worm disease, plague,
strep throat

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.

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?”
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?



PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:

NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award


Supported by NIEHS grant # ES06694

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